Clean up developer mode logic

Fixes the ability to deploy a venv in cases where:
1) developer_mode is not enabled
2) A cached venv is not downloaded from the repo server

Additional cleanup to the developer_mode venv deployment
logic is implemented by adding a *_venv_download var
which is used to decouple developer_mode from the
cached venv extraction process so that a deployer
can force venv builds in-place (disable cached
venv usage) without enabling developer mode
constraints.

Change-Id: Iea13582d7344e343f60439500ef5e38dfbf1f1c1

defaults/main.yml

@@ -51,6 +51,9 @@ horizon_developer_constraints:
 horizon_venv_tag: untagged
 horizon_bin: "/openstack/venvs/horizon-{{ horizon_venv_tag }}/bin"
 
+# venv_download, even when true, will use the fallback method of building the
+# venv from scratch if the venv download fails.
+horizon_venv_download: "{{ not horizon_developer_mode | bool }}"
 horizon_venv_download_url: http://127.0.0.1/venvs/untagged/ubuntu/horizon.tgz
 
 ## System info

tasks/horizon_install.yml

@@ -81,7 +81,7 @@
     dest: "/var/cache/{{ horizon_venv_download_url | basename }}"
     checksum: "sha1:{{ lookup('url', horizon_venv_download_url | replace('tgz', 'checksum')) }}"
   register: horizon_get_venv
-  when: not horizon_developer_mode | bool
+  when: horizon_venv_download | bool
 
 - name: Remove existing venv
   file:
@@ -95,18 +95,14 @@
     state: directory
     mode: "0755"
   register: horizon_venv_dir
-  when:
-    - not horizon_developer_mode | bool
-    - horizon_get_venv | changed
+  when: horizon_get_venv | changed
 
 - name: Unarchive pre-built venv
   unarchive:
     src: "/var/cache/{{ horizon_venv_download_url | basename }}"
     dest: "{{ horizon_bin | dirname }}"
     copy: "no"
-  when:
-    - not horizon_developer_mode | bool
-    - horizon_get_venv | changed or horizon_venv_dir | changed
+  when: horizon_get_venv | changed
   notify: Restart apache2
 
 - name: Install pip packages
@@ -123,7 +119,7 @@
   until: install_packages|success
   retries: 5
   delay: 2
-  when: horizon_developer_mode | bool
+  when: horizon_get_venv | failed or horizon_get_venv | skipped
   notify: Restart apache2
 
 - name: Install optional pip packages
@@ -148,15 +144,12 @@
     state: "absent"
   when:
     - ansible_pkg_mgr == 'yum'
-    - not horizon_developer_mode | bool
-    - horizon_get_venv | changed or horizon_venv_dir | changed
+    - horizon_get_venv | changed
 
 - name: Update virtualenv path
   command: >
     virtualenv-tools --update-path=auto --reinitialize {{ horizon_bin | dirname }}
-  when:
-    - not horizon_developer_mode | bool
-    - horizon_get_venv | changed or horizon_venv_dir | changed
+  when: horizon_get_venv | changed
 
 - name: Create horizon link for venv
   file: