create an interface to read cb version

certbot-dns-dnsimple/snap/hooks/post-refresh

@@ -1,7 +1,7 @@
 #!/bin/sh -e
 
 # get certbot version
-cb_installed=$(snap info certbot | grep -oP 'installed:\s+\K\d+.\d+.\d(?=-)')
+cb_installed=$(grep -oP 'installed:\s+\K\d+.\d+.\d(?=-)' $SNAP/certbot-version/certbot)
 # get required certbot version for plugin
 cb_required=$(grep -oP "certbot>=\K.*(?=')" $SNAP/setup.py)
 

certbot-dns-dnsimple/snap/snapcraft.yaml

@@ -27,3 +27,11 @@ slots:
     content: certbot-1
     read:
       - $SNAP/lib/python3.8/site-packages
+
+hooks:
+  post-refresh:
+    plugs:
+      certbot-version:
+        interface: content
+        content: version-1
+        target: $SNAP/certbot-version

snap/snapcraft.yaml

@@ -90,3 +90,9 @@ plugs:
     interface: content
     content: certbot-1
     target: $SNAP/certbot-plugin
+
+slots:
+  version:
+    interface: content
+    content: version-1
+    read: $SNAP/bin/certbot