Add whitelist for when to use custom PPA

Right now the PPA is only serving newer versions of python2 than Ubuntu
PPAs are providing for trusty and precise. Since the version provided
for xenial is new enough, there's no reason to use a custom PPA, and
this saves us from having to support more unnecessary Ubuntu releases in
our PPA.

playbooks/roles/aws/tasks/main.yml

@@ -87,13 +87,27 @@
  # and add a custom motd.  These do not require an
  # ssh restart
  # Only needed for EC2 instances.
-- name: Update the ssh motd on Ubuntu
-  file:
+- name: Check if files exist so the next task doesn't fail
+  stat:
     path: "{{ item }}"
-    mode: "0644"
-  when: (vagrant_home_dir.stat.exists == false) and (ansible_distribution in common_debian_variants)
+  register: motd_files_exist
   with_items:
     - "/etc/update-motd.d/10-help-text"
     - "/usr/share/landscape/landscape-sysinfo.wrapper"
     - "/etc/update-motd.d/51-cloudguest"
     - "/etc/update-motd.d/91-release-upgrade"
+
+- name: Update the ssh motd on Ubuntu
+  file:
+    path: "{{ item.0 }}"
+    mode: "0644"
+  when: >
+    vagrant_home_dir.stat.exists == false and
+    ansible_distribution in common_debian_variants and
+    item.1.stat.exists
+  with_together:
+    - - "/etc/update-motd.d/10-help-text"
+      - "/usr/share/landscape/landscape-sysinfo.wrapper"
+      - "/etc/update-motd.d/51-cloudguest"
+      - "/etc/update-motd.d/91-release-upgrade"
+    - motd_files_exist.results

playbooks/roles/common/tasks/main.yml

@@ -34,24 +34,32 @@
     path: /home/vagrant
   register: vagrant_home_dir
 
+# Ensure that we get a current version of Git
+# GitHub requires version 1.7.10 or later
+# https://help.github.com/articles/https-cloning-errors
+- name: Add git apt repository
+  apt_repository:
+    repo: "{{ common_git_ppa }}"
+  when: ansible_distribution in common_debian_variants
+
+
+# Ensure that we get the latest version of python 2.7
 - name: add edx ppa apt key
   apt_key:
     id: "{{ COMMON_EDX_PPA_KEY_ID }}"
     keyserver: "{{ COMMON_EDX_PPA_KEY_SERVER }}"
     state: "present"
-  when: ansible_distribution in common_debian_variants
-
+  when: >
+    ansible_distribution in common_debian_variants and
+    ansible_distribution_release in common_custom_ppa_releases
 
-# Ensure that we get a current version of Git and latest version of python 2.7
-# GitHub requires version 1.7.10 or later
-# https://help.github.com/articles/https-cloning-errors
-- name: Add git apt repository
+- name: Add custom edX PPA
   apt_repository:
-    repo: "{{ item }}"
-  with_items:
-    - "{{ common_git_ppa }}"
-    - "{{ COMMON_EDX_PPA }}"
-  when: ansible_distribution in common_debian_variants
+    repo: "{{ COMMON_EDX_PPA }}"
+  when: >
+    ansible_distribution in common_debian_variants and
+    ansible_distribution_release in common_custom_ppa_releases
+
 
 - name: Install role-independent useful system packages
   # do this before log dir setup; rsyslog package guarantees syslog user present
@@ -63,6 +71,17 @@
   with_items: "{{ common_debian_pkgs }}"
   when: ansible_distribution in common_debian_variants
 
+- name: Install role-independent useful system packages from custom PPA
+  apt:
+    name: "{{ item }}"
+    install_recommends: yes
+    state: present 
+    update_cache: yes
+  with_items: "{{ common_custom_debian_pkgs }}"
+  when: >
+    ansible_distribution in common_debian_variants and 
+    ansible_distribution_release in common_custom_ppa_releases
+
 - name: Install role-independent useful system packages
   yum:
     name: "{{ item }}"

playbooks/roles/common_vars/defaults/main.yml

@@ -112,10 +112,13 @@ common_debian_pkgs:
   - rsyslog
   - git
   - unzip
-  - "python2.7=2.7.10-0+{{ ansible_distribution_release }}1"
   - python-pip
   - python2.7-dev
-  
+
+# Packages that should be installed from our custom PPA, i.e. COMMON_EDX_PPA 
+common_custom_debian_pkgs:
+  - "python2.7=2.7.10-0+{{ ansible_distribution_release }}1"
+
 common_pip_pkgs:
   - pip==8.1.2
   - setuptools==24.0.3
@@ -147,6 +150,11 @@ common_debian_variants:
   - Ubuntu
   - Debian
 
+# Only attempt to use our custom PPA for these releases
+common_custom_ppa_releases:
+  - precise
+  - trusty
+
 common_redhat_variants:
   - CentOS
   - Red Hat Enterprise Linux