Setup cron build with specific jobs (#6661)

Fixes #6659

It appears that the conditional statement if: cron = type works as expected:

on a push event, jobs marked with this statement are completely ignored
on a cron event, these jobs are executed
This PR takes advantages of it, by integrating the specific environments from test-everything branch to be merged into master, and add the conditional statement to execute them only during cron builds.

Once this PR is merged, a cron job can be set to build master at the appropriate time of the day, and test-everything will not be needed anymore.

For execution examples from this branch, see:

during a push event: https://travis-ci.org/adferrand/certbot/builds/480127828
during a cron event: https://travis-ci.org/adferrand/certbot/builds/480130236

* Use the conditional expression in travis.yml to execute jobs from test-everything only during cron executions.

* Update .travis.yml

* Update .travis.yml

* Remove before_install

.travis.yml

@@ -4,15 +4,13 @@ cache:
     directories:
         - $HOME/.cache/pip
 
-before_install:
-  - '([ $TRAVIS_OS_NAME == linux ] && dpkg -s libaugeas0) || (brew update && brew install augeas python3 && brew upgrade python && brew link python)'
-
 before_script:
   - 'if [ $TRAVIS_OS_NAME = osx ] ; then ulimit -n 1024 ; fi'
   - export TOX_TESTENV_PASSENV=TRAVIS
 
 matrix:
   include:
+    # These environments are always executed
     - python: "2.7"
       env: BOULDER_INTEGRATION=v1 INTEGRATION_TEST=all TOXENV=py27_install
       sudo: required
@@ -64,6 +62,109 @@ matrix:
     - python: "2.7"
       env: TOXENV=nginxroundtrip
 
+    # These environments are executed on cron events only
+    - python: "2.7"
+      env: BOULDER_INTEGRATION=v1 INTEGRATION_TEST=certbot TOXENV=py27-certbot-oldest
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "2.7"
+      env: BOULDER_INTEGRATION=v2 INTEGRATION_TEST=certbot TOXENV=py27-certbot-oldest
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "2.7"
+      env: BOULDER_INTEGRATION=v1 INTEGRATION_TEST=nginx TOXENV=py27-nginx-oldest
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "2.7"
+      env: BOULDER_INTEGRATION=v2 INTEGRATION_TEST=nginx TOXENV=py27-nginx-oldest
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "3.4"
+      env: TOXENV=py34 BOULDER_INTEGRATION=v1
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "3.4"
+      env: TOXENV=py34 BOULDER_INTEGRATION=v2
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "3.5"
+      env: TOXENV=py35 BOULDER_INTEGRATION=v1
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "3.5"
+      env: TOXENV=py35 BOULDER_INTEGRATION=v2
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "3.6"
+      env: TOXENV=py36 BOULDER_INTEGRATION=v1
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "3.6"
+      env: TOXENV=py36 BOULDER_INTEGRATION=v2
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "3.7"
+      dist: xenial
+      env: TOXENV=py37 BOULDER_INTEGRATION=v1
+      sudo: required
+      services: docker
+      if: type = cron
+    - python: "3.7"
+      dist: xenial
+      env: TOXENV=py37 BOULDER_INTEGRATION=v2
+      sudo: required
+      services: docker
+      if: type = cron
+    - sudo: required
+      env: TOXENV=le_auto_precise
+      services: docker
+      if: type = cron
+    - sudo: required
+      env: TOXENV=le_auto_wheezy
+      services: docker
+      if: type = cron
+    - sudo: required
+      env: TOXENV=le_auto_centos6
+      services: docker
+      if: type = cron
+    - sudo: required
+      env: TOXENV=docker_dev
+      services: docker
+      addons:
+        apt:
+          packages:  # don't install nginx and apache
+            - libaugeas0
+      if: type = cron
+    - language: generic
+      env: TOXENV=py27
+      os: osx
+      addons:
+        homebrew:
+          packages:
+            - augeas
+            - python2
+      if: type = cron
+    - language: generic
+      env: TOXENV=py3
+      os: osx
+      addons:
+        homebrew:
+          packages:
+            - augeas
+            - python3
+      if: type = cron
+
+
 
 # Only build pushes to the master branch, PRs, and branches beginning with
 # `test-` or of the form `digit(s).digit(s).x`. This reduces the number of