Isolate Ansible from the deployment host

This change allows Ansible to be installed and executed from within
a virtual environment.

Closes-Bug: 1431324
Implements: blueprint ansible-2-1-support
Change-Id: I2fb19dd8218753f75bd7550ed7ba9b79f777083d
Signed-off-by: Kevin Carter <kevin.carter@rackspace.com>

releasenotes/notes/isolate-ansible-3e8fcfdff9962a9b.yaml

@@ -0,0 +1,9 @@
+---
+features:
+  - To ensure the deployment system remains clean the Ansible execution environment is
+    contained within a virtual environment. The virtual environment is created at
+    "/opt/ansible-runtime" and the "ansible.*" CLI commands are linked within /usr/local/bin
+    to ensure there is no interruption in the deployer workflow.
+deprecations:
+  - Installation of Ansible on the root system, outside of a virtual environment, will
+    no longer be supported.

requirements.txt

@@ -1,5 +1,8 @@
 netaddr>=0.7.12         # playbooks/inventory/dynamic_inventory.py
 PrettyTable>=0.7,<0.8   # scripts/inventory-manage.py
+pycrypto>=2.6           # scripts/pw-token-gen.py
+PyYAML>=3.1.0           # scripts/pw-token-gen.py
+virtualenv>=14.0.0      # Used for Ansible isolation
 ###
 ### These are pinned to ensure exactly the same behaviour forever!   ###
 ### These pins are updated through the sources-branch-updater script ###

scripts/bootstrap-ansible.sh

@@ -83,17 +83,25 @@ if [ ! $(which "$PIP_COMMAND") ]; then
   PIP_COMMAND=pip
 fi
 
-# Install requirements if there are any
-if [ -f "requirements.txt" ];then
-  # When upgrading there will already be a pip.conf file locking pip down to the repo server, in such cases it may be
-  # necessary to use --isolated because the repo server does not meet the specified requirements.
-  $PIP_COMMAND install $PIP_OPTS -r requirements.txt || $PIP_COMMAND install --isolated $PIP_OPTS -r requirements.txt
-fi
-
-# Install ansible
 # When upgrading there will already be a pip.conf file locking pip down to the repo server, in such cases it may be
 # necessary to use --isolated because the repo server does not meet the specified requirements.
-$PIP_COMMAND install $PIP_OPTS "${ANSIBLE_WORKING_DIR}" || $PIP_COMMAND install --isolated $PIP_OPTS "${ANSIBLE_WORKING_DIR}"
+$PIP_COMMAND install $PIP_OPTS -r requirements.txt || $PIP_COMMAND install --isolated $PIP_OPTS -r requirements.txt
+
+# Create a Virtualenv for the Ansible runtime
+PYTHON_EXEC_PATH="$(which python2 || which python)"
+virtualenv --always-copy --system-site-packages --python="${PYTHON_EXEC_PATH}" /opt/ansible-runtime
+
+# Install ansible
+PIP_OPTS+=" --upgrade"
+PIP_COMMAND="/opt/ansible-runtime/bin/pip"
+# When upgrading there will already be a pip.conf file locking pip down to the repo server, in such cases it may be
+# necessary to use --isolated because the repo server does not meet the specified requirements.
+$PIP_COMMAND install $PIP_OPTS -r requirements.txt "${ANSIBLE_WORKING_DIR}" || $PIP_COMMAND install --isolated $PIP_OPTS "${ANSIBLE_WORKING_DIR}"
+
+# Link the venv installation of Ansible to the local path
+pushd /usr/local/bin
+    find /opt/ansible-runtime/bin/ -name 'ansible*' -exec ln -sf {} \;
+popd
 
 # Update dependent roles
 if [ -f "${ANSIBLE_ROLE_FILE}" ]; then

test-requirements.txt

@@ -7,6 +7,7 @@ hacking>=0.10.0,<0.11
 mccabe==0.2.1 # capped for flake8
 pep8==1.5.7
 pyflakes==0.8.1
+virtualenv>=14.0.0
 
 # this is required for the docs build jobs
 sphinx!=1.2.0,!=1.3b1,<1.3,>=1.1.2