diff --git a/certbot-dns-cloudflare/setup.py b/certbot-dns-cloudflare/setup.py
index 60add8ae5..2791f423d 100644
--- a/certbot-dns-cloudflare/setup.py
+++ b/certbot-dns-cloudflare/setup.py
@@ -17,14 +17,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.29.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-cloudflare/snap/hooks/post-refresh b/certbot-dns-cloudflare/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-cloudflare/snap/hooks/post-refresh
+++ b/certbot-dns-cloudflare/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-cloudflare/snap/snapcraft.yaml b/certbot-dns-cloudflare/snap/snapcraft.yaml
index 8697d6848..81fa2d5c7 100644
--- a/certbot-dns-cloudflare/snap/snapcraft.yaml
+++ b/certbot-dns-cloudflare/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-cloudxns/setup.py b/certbot-dns-cloudxns/setup.py
index 0e70800ce..7a5c7ff3d 100644
--- a/certbot-dns-cloudxns/setup.py
+++ b/certbot-dns-cloudxns/setup.py
@@ -17,14 +17,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.31.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-cloudxns/snap/hooks/post-refresh b/certbot-dns-cloudxns/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-cloudxns/snap/hooks/post-refresh
+++ b/certbot-dns-cloudxns/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-cloudxns/snap/snapcraft.yaml b/certbot-dns-cloudxns/snap/snapcraft.yaml
index 34fef741a..1fcaef8b9 100644
--- a/certbot-dns-cloudxns/snap/snapcraft.yaml
+++ b/certbot-dns-cloudxns/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-digitalocean/setup.py b/certbot-dns-digitalocean/setup.py
index 4fe54b0f8..267999217 100644
--- a/certbot-dns-digitalocean/setup.py
+++ b/certbot-dns-digitalocean/setup.py
@@ -18,14 +18,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.29.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-digitalocean/snap/hooks/post-refresh b/certbot-dns-digitalocean/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-digitalocean/snap/hooks/post-refresh
+++ b/certbot-dns-digitalocean/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-digitalocean/snap/snapcraft.yaml b/certbot-dns-digitalocean/snap/snapcraft.yaml
index d8a950d58..b6f6506e2 100644
--- a/certbot-dns-digitalocean/snap/snapcraft.yaml
+++ b/certbot-dns-digitalocean/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-dnsimple/setup.py b/certbot-dns-dnsimple/setup.py
index f23c42521..acb951e83 100644
--- a/certbot-dns-dnsimple/setup.py
+++ b/certbot-dns-dnsimple/setup.py
@@ -16,14 +16,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.31.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-dnsimple/snap/hooks/post-refresh b/certbot-dns-dnsimple/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-dnsimple/snap/hooks/post-refresh
+++ b/certbot-dns-dnsimple/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-dnsimple/snap/snapcraft.yaml b/certbot-dns-dnsimple/snap/snapcraft.yaml
index 1961c8afc..2d7a1d5d2 100644
--- a/certbot-dns-dnsimple/snap/snapcraft.yaml
+++ b/certbot-dns-dnsimple/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-dnsmadeeasy/setup.py b/certbot-dns-dnsmadeeasy/setup.py
index a0ba4ac28..7940e9fc6 100644
--- a/certbot-dns-dnsmadeeasy/setup.py
+++ b/certbot-dns-dnsmadeeasy/setup.py
@@ -17,14 +17,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.31.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-dnsmadeeasy/snap/hooks/post-refresh b/certbot-dns-dnsmadeeasy/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-dnsmadeeasy/snap/hooks/post-refresh
+++ b/certbot-dns-dnsmadeeasy/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-dnsmadeeasy/snap/snapcraft.yaml b/certbot-dns-dnsmadeeasy/snap/snapcraft.yaml
index 565cabe0d..75f083732 100644
--- a/certbot-dns-dnsmadeeasy/snap/snapcraft.yaml
+++ b/certbot-dns-dnsmadeeasy/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-gehirn/setup.py b/certbot-dns-gehirn/setup.py
index a021bffce..d93acbe60 100644
--- a/certbot-dns-gehirn/setup.py
+++ b/certbot-dns-gehirn/setup.py
@@ -16,14 +16,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.31.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-gehirn/snap/hooks/post-refresh b/certbot-dns-gehirn/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-gehirn/snap/hooks/post-refresh
+++ b/certbot-dns-gehirn/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-gehirn/snap/snapcraft.yaml b/certbot-dns-gehirn/snap/snapcraft.yaml
index dbfef38fb..ea19f045b 100644
--- a/certbot-dns-gehirn/snap/snapcraft.yaml
+++ b/certbot-dns-gehirn/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-google/setup.py b/certbot-dns-google/setup.py
index 0c559585b..d9e508494 100644
--- a/certbot-dns-google/setup.py
+++ b/certbot-dns-google/setup.py
@@ -20,14 +20,16 @@ install_requires = [
     'httplib2'
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.29.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-google/snap/hooks/post-refresh b/certbot-dns-google/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-google/snap/hooks/post-refresh
+++ b/certbot-dns-google/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-google/snap/snapcraft.yaml b/certbot-dns-google/snap/snapcraft.yaml
index 7b31ac8f6..6a60a9426 100644
--- a/certbot-dns-google/snap/snapcraft.yaml
+++ b/certbot-dns-google/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-linode/setup.py b/certbot-dns-linode/setup.py
index 8e765bd8f..1a1e3f973 100644
--- a/certbot-dns-linode/setup.py
+++ b/certbot-dns-linode/setup.py
@@ -16,14 +16,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.31.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-linode/snap/hooks/post-refresh b/certbot-dns-linode/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-linode/snap/hooks/post-refresh
+++ b/certbot-dns-linode/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-linode/snap/snapcraft.yaml b/certbot-dns-linode/snap/snapcraft.yaml
index 0e8196130..c6a30c7f2 100644
--- a/certbot-dns-linode/snap/snapcraft.yaml
+++ b/certbot-dns-linode/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-luadns/setup.py b/certbot-dns-luadns/setup.py
index 57c5011eb..0ff9fb249 100644
--- a/certbot-dns-luadns/setup.py
+++ b/certbot-dns-luadns/setup.py
@@ -17,14 +17,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.31.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-luadns/snap/hooks/post-refresh b/certbot-dns-luadns/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-luadns/snap/hooks/post-refresh
+++ b/certbot-dns-luadns/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-luadns/snap/snapcraft.yaml b/certbot-dns-luadns/snap/snapcraft.yaml
index 53c6dff2d..4cd90abae 100644
--- a/certbot-dns-luadns/snap/snapcraft.yaml
+++ b/certbot-dns-luadns/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-nsone/setup.py b/certbot-dns-nsone/setup.py
index b8d33bb60..2b37a4c18 100644
--- a/certbot-dns-nsone/setup.py
+++ b/certbot-dns-nsone/setup.py
@@ -17,14 +17,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.31.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-nsone/snap/hooks/post-refresh b/certbot-dns-nsone/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-nsone/snap/hooks/post-refresh
+++ b/certbot-dns-nsone/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-nsone/snap/snapcraft.yaml b/certbot-dns-nsone/snap/snapcraft.yaml
index ba8ae03fd..88c29226a 100644
--- a/certbot-dns-nsone/snap/snapcraft.yaml
+++ b/certbot-dns-nsone/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-ovh/setup.py b/certbot-dns-ovh/setup.py
index e8b2ffd1e..a8baea0f1 100644
--- a/certbot-dns-ovh/setup.py
+++ b/certbot-dns-ovh/setup.py
@@ -17,14 +17,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.31.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-ovh/snap/hooks/post-refresh b/certbot-dns-ovh/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-ovh/snap/hooks/post-refresh
+++ b/certbot-dns-ovh/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-ovh/snap/snapcraft.yaml b/certbot-dns-ovh/snap/snapcraft.yaml
index bf5801797..733737884 100644
--- a/certbot-dns-ovh/snap/snapcraft.yaml
+++ b/certbot-dns-ovh/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-rfc2136/setup.py b/certbot-dns-rfc2136/setup.py
index 83939f796..09cce6a21 100644
--- a/certbot-dns-rfc2136/setup.py
+++ b/certbot-dns-rfc2136/setup.py
@@ -17,14 +17,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.29.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-rfc2136/snap/hooks/post-refresh b/certbot-dns-rfc2136/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-rfc2136/snap/hooks/post-refresh
+++ b/certbot-dns-rfc2136/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-rfc2136/snap/snapcraft.yaml b/certbot-dns-rfc2136/snap/snapcraft.yaml
index 7e60d067b..2726c2974 100644
--- a/certbot-dns-rfc2136/snap/snapcraft.yaml
+++ b/certbot-dns-rfc2136/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-route53/setup.py b/certbot-dns-route53/setup.py
index 893f40340..5d2b0494d 100644
--- a/certbot-dns-route53/setup.py
+++ b/certbot-dns-route53/setup.py
@@ -17,14 +17,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.29.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-route53/snap/hooks/post-refresh b/certbot-dns-route53/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-route53/snap/hooks/post-refresh
+++ b/certbot-dns-route53/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-route53/snap/snapcraft.yaml b/certbot-dns-route53/snap/snapcraft.yaml
index 9bb15229d..78602ff02 100644
--- a/certbot-dns-route53/snap/snapcraft.yaml
+++ b/certbot-dns-route53/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/certbot-dns-sakuracloud/setup.py b/certbot-dns-sakuracloud/setup.py
index cb6785ecd..812be34ba 100644
--- a/certbot-dns-sakuracloud/setup.py
+++ b/certbot-dns-sakuracloud/setup.py
@@ -16,14 +16,16 @@ install_requires = [
     'zope.interface',
 ]
 
-if not os.environ.get('EXCLUDE_CERTBOT_DEPS'):
+if not os.environ.get('SNAP_BUILD'):
     install_requires.extend([
         'acme>=0.31.0',
         'certbot>=1.1.0',
     ])
 elif 'bdist_wheel' in sys.argv[1:]:
-    raise RuntimeError('Unset EXCLUDE_CERTBOT_DEPS when building wheels '
+    raise RuntimeError('Unset SNAP_BUILD when building wheels '
                        'to include certbot dependencies.')
+if os.environ.get('SNAP_BUILD'):
+    install_requires.append('packaging')
 
 setuptools_known_environment_markers = (LooseVersion(setuptools_version) >= LooseVersion('36.2'))
 if setuptools_known_environment_markers:
diff --git a/certbot-dns-sakuracloud/snap/hooks/post-refresh b/certbot-dns-sakuracloud/snap/hooks/post-refresh
index 9791704c0..c4688009c 100644
--- a/certbot-dns-sakuracloud/snap/hooks/post-refresh
+++ b/certbot-dns-sakuracloud/snap/hooks/post-refresh
@@ -13,7 +13,7 @@ cb_installed=$(cat $SNAP/certbot-shared/certbot-version.txt)
 cb_required=$(grep -oP "version = '\K.*(?=')" $SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
+/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if  version.parse('$cb_installed') < version.parse('$cb_required') else sys.exit(0)" || exit_code=$?
 if [ "$exit_code" -eq 1 ]; then
   echo "Certbot is version $cb_installed but needs to be at least $cb_required before"     "this plugin can be updated; will try again on next refresh."
   exit 1
diff --git a/certbot-dns-sakuracloud/snap/snapcraft.yaml b/certbot-dns-sakuracloud/snap/snapcraft.yaml
index 2727afdcc..ebcf8bea7 100644
--- a/certbot-dns-sakuracloud/snap/snapcraft.yaml
+++ b/certbot-dns-sakuracloud/snap/snapcraft.yaml
@@ -16,7 +16,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version `grep ^version $SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .
diff --git a/tools/generate_dnsplugins_postrefreshhook.sh b/tools/generate_dnsplugins_postrefreshhook.sh
index a691071fa..a9636cd41 100755
--- a/tools/generate_dnsplugins_postrefreshhook.sh
+++ b/tools/generate_dnsplugins_postrefreshhook.sh
@@ -24,7 +24,7 @@ cb_installed=\$(cat \$SNAP/certbot-shared/certbot-version.txt)
 cb_required=\$(grep -oP "version = '\K.*(?=')" \$SNAP/setup.py)
 
 
-python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if\
+$SNAP/bin/python3 -c "import sys; from setuptools._vendor.packaging import version; sys.exit(1) if\
   version.parse('\$cb_installed') < version.parse('\$cb_required') else sys.exit(0)" || exit_code=\$?
 if [ "\$exit_code" -eq 1 ]; then
   echo "Certbot is version \$cb_installed but needs to be at least \$cb_required before" \
diff --git a/tools/generate_dnsplugins_snapcraft.sh b/tools/generate_dnsplugins_snapcraft.sh
index df199f808..96e79d681 100755
--- a/tools/generate_dnsplugins_snapcraft.sh
+++ b/tools/generate_dnsplugins_snapcraft.sh
@@ -28,7 +28,7 @@ parts:
         snapcraftctl pull
         snapcraftctl set-version \`grep ^version \$SNAPCRAFT_PART_SRC/setup.py | cut -f2 -d= | tr -d "'[:space:]"\`
     build-environment:
-      - EXCLUDE_CERTBOT_DEPS: "True"
+      - SNAP_BUILD: "True"
   certbot-metadata:
     plugin: dump
     source: .