Optimise venv fetch mechanism

Unnecessary tasks are removed and the ability to ignore a venv
download failure is removed as this is not necessary or desirable.
It is better for the download to fail and the playbook execution
to stop immediately so that the failure point is exposed.

Change-Id: I2dbe74353e22368074bc3219605e9c4b2da896e8

meta/main.yml

@@ -4,7 +4,7 @@ galaxy_info:
   description: Installation and setup of sahara
   company: LSD/UFCG
   license: Apache2
-  min_ansible_version: 1.9.4
+  min_ansible_version: 2.0
   platforms:
     - name: Ubuntu
       versions:

tasks/sahara_install.yml

@@ -37,34 +37,19 @@
   retries: 5
   delay: 2
 
-- name: Get remote venv checksum
-  uri:
-    url: "{{ sahara_venv_download_url | replace('tgz', 'checksum') }}"
-    return_content: True
-  when:
-    - not sahara_developer_mode | bool
-  register: remote_venv_checksum
-
 - name: Attempt venv download
   get_url:
     url: "{{ sahara_venv_download_url }}"
     dest: "/var/cache/{{ sahara_venv_download_url | basename }}"
-    checksum: "sha1:{{ remote_venv_checksum.content }}"
-  failed_when: false
-  register: get_venv
-  when:
-    - not sahara_developer_mode | bool
-
-- name: Set sahara get_venv fact
-  set_fact:
-    sahara_get_venv: "{{ get_venv }}"
+    checksum: "sha1:{{ lookup('url', sahara_venv_download_url | replace('tgz', 'checksum')) }}"
+  register: sahara_get_venv
+  when: not sahara_developer_mode | bool
 
 - name: Remove existing venv
   file:
     path: "{{ sahara_bin | dirname }}"
     state: absent
-  when:
-    - sahara_get_venv | changed
+  when: sahara_get_venv | changed
 
 - name: Create sahara venv dir
   file:
@@ -97,8 +82,7 @@
   until: install_packages|success
   retries: 5
   delay: 2
-  when:
-    - sahara_get_venv | failed or sahara_developer_mode | bool
+  when: sahara_developer_mode | bool
   notify:
     - Restart sahara services
 
@@ -107,4 +91,4 @@
     virtualenv-tools --update-path=auto {{ sahara_bin | dirname }}
   when:
     - not sahara_developer_mode | bool
-    - sahara_get_venv | success
+    - sahara_get_venv | changed or sahara_venv_dir | changed