Run source-install tests for Ubuntu 14.04 as there's no package available

.travis.yml

@@ -17,7 +17,7 @@ env:
   - distro: ubuntu1404
     init: /sbin/init
     run_opts: ""
-    playbook: test.yml
+    playbook: test-source-install.yml
   - distro: ubuntu1204
     init: /sbin/init
     run_opts: ""

tests/test-source-install.yml

@@ -5,10 +5,19 @@
     certbot_install_from_source: yes
 
   pre_tasks:
+    - name: Update apt cache.
+      apt: update_cache=yes cache_valid_time=600
+      when: ansible_os_family == 'Debian'
+      changed_when: false
+
     - name: Install cron (RedHat).
       yum: name=cronie state=present
       when: ansible_os_family == 'RedHat'
 
+    - name: Install cron (Debian).
+      apt: name=cron state=present
+      when: ansible_os_family == 'Debian'
+
   roles:
     - geerlingguy.git
     - role_under_test