Add Python 3.7 tests (#6179)

* Remove apacheconftest packages.

The apacheconftests handle installing Apache dependencies, so let's remove it from the general case.

* We don't need to run dpkg -s in before_install.

* Remove augeas sources.

We only needed it for Ubuntu Precise which is dead and it doesn't work in Ubuntu Xenial.

* Upgrade Python 3.6 tests to 3.7.

Let's continue the approach of testing on the oldest and newest versions of Python 3. We will continue testing on Python 3.6 in the nightly tests.

* Revert "We don't need to run dpkg -s in before_install."

This reverts commit e5d35099a7.

* let apacheconftest handle deps

.travis.yml

@@ -41,8 +41,9 @@ matrix:
       env: TOXENV=py34
       sudo: required
       services: docker
-    - python: "3.6"
-      env: TOXENV=py36
+    - python: "3.7"
+      dist: xenial
+      env: TOXENV=py37
       sudo: required
       services: docker
     - sudo: required
@@ -77,8 +78,6 @@ sudo: false
 
 addons:
   apt:
-    sources:
-    - augeas
     packages:  # Keep in sync with letsencrypt-auto-source/pieces/bootstrappers/deb_common.sh and Boulder.
     - python-dev
     - python-virtualenv
@@ -90,10 +89,6 @@ addons:
     # For certbot-nginx integration testing
     - nginx-light
     - openssl
-    # for apacheconftest
-    - apache2
-    - libapache2-mod-wsgi
-    - libapache2-mod-macro
 
 install: "travis_retry $(command -v pip || command -v pip3) install tox coveralls"
 script:

certbot-apache/certbot_apache/tests/apache-conf-files/apache-conf-test

@@ -46,6 +46,7 @@ function Cleanup() {
 
 # if our environment asks us to enable modules, do our best!
 if [ "$1" = --debian-modules ] ; then
+    sudo apt-get install -y apache2
     sudo apt-get install -y libapache2-mod-wsgi
     sudo apt-get install -y libapache2-mod-macro