ensure-pip : fix Xenial exported virtualenv command

This is a fix for Id8347b6b09735659a7ed9bbe7f9d2798fbec9620 which did
not specify the full path in ensure_pip_virtualenv_command for Xenial.

This slipped by testing because there we check
ensure_pip_virtualenv_command runs under a shell:, but not when called
as the argument to the pip: module (which exec's it differently and
requires the full path).  Update testing to do that too.

Change-Id: I65ff5ce913917079ab2fc1d88c56d1c0a24ea83e

roles/ensure-pip/tasks/main.yaml

@@ -84,5 +84,5 @@
 
     - name: Override virtualenv
       set_fact:
-        ensure_pip_virtualenv_command: 'virtualenv -p python3'
+        ensure_pip_virtualenv_command: '/usr/local/bin/virtualenv -p python3'
       when: _pip_check.rc == 0

test-playbooks/ensure-pip.yaml

@@ -1,24 +1,32 @@
 - hosts: all
   tasks:
+    # ensure-pip
+
     - name: Include ensure-pip
       include_role:
         name: ensure-pip
 
-    - name: Sanity check provided virtualenv command works
-      shell: |
-        tmp_venv=$(mktemp -d -t venv-XXXXXXXXXX)
-        trap "rm -rf $tmp_venv" EXIT
-        {{ ensure_pip_virtualenv_command }} $tmp_venv
-        $tmp_venv/bin/pip install tox
-      failed_when: false
-      register: _venv_sanity
+    - name: Create temp directory
+      tempfile:
+        state: directory
+        suffix: venv-test
+      register: _tmp_venv
 
-    - name: Assert pip venv sanity check
-      fail:
-        msg: 'The virtualenv_command: "{{ ensure_pip_virtualenv_command }}" does not appear to work!'
-      when:
-        - _venv_sanity.rc != 0
+    - name: Sanity check provided virtualenv command installs
+      pip:
+        name: tox
+        virtualenv_command: '{{ ensure_pip_virtualenv_command }}'
+        virtualenv: '{{ _tmp_venv.path }}'
 
+    - name: Sanity check installed command runs without error
+      command: '{{ _tmp_venv.path }}/bin/tox --version'
+
+    - name: Remove tmpdir
+      file:
+        path: '{{ _tmp_venv.path }}'
+        state: absent
+
+    # ensure-virtualenv
     - name: Include ensure-virtualenv
       include_role:
         name: ensure-virtualenv