Use a venv to build the python wheels

To limit the python packages installed on the host,
all packages installed by pip are implemented into
a venv.

While many of the repo_pip_packages may be available
via distribution packages, the versions vary wildly.
We therefore opt to use a venv instead to keep things
simple.

This reduces the requirement on the host to *only*
require the virtualenv package which is installed in
the openstack_hosts role.

The 'virtualenv' package is removed from the list as
it is not used.

Change-Id: I0619f51960e23756df7010d476d70f55ceda8441

defaults/main.yml

@@ -112,12 +112,15 @@ repo_build_venv_command_options: >-
   --no-setuptools
   --no-wheel
 
+# Path to the repo build venv binaries
+repo_build_bin: "/openstack/venvs/repo-build-{{ repo_build_release_tag }}/bin"
+
+# Python packages to install into the repo build venv
 repo_pip_packages:
   - cython
   - pbr
   - requests
   - urllib3
-  - virtualenv
   - wheel
 
 repo_build_store_pip_sources: false

tasks/repo_build_prepare.yml

@@ -102,6 +102,8 @@
       pip:
         name: "{{ repo_pip_packages }}"
         state: "{{ repo_build_pip_package_state }}"
+        virtualenv: "{{ repo_build_bin | dirname }}"
+        virtualenv_site_packages: "no"
         extra_args: >-
           --constraint {{ repo_build_release_path }}/requirements_constraints.txt
           {{ pip_install_options }}
@@ -114,6 +116,8 @@
       pip:
         name: "{{ repo_pip_packages }}"
         state: "{{ repo_build_pip_package_state }}"
+        virtualenv: "{{ repo_build_bin | dirname }}"
+        virtualenv_site_packages: "no"
         extra_args: >-
           --index-url {{ repo_build_pip_default_index }}
           --trusted-host {{ repo_build_pip_default_index | netloc_no_port }}

tasks/repo_build_wheels.yml

@@ -41,7 +41,8 @@
 - name: Download requirement pip sources
   shell: >-
     set -o pipefail;
-    yes i | pip install --timeout {{ repo_build_timeout }}
+    yes i | {{ repo_build_bin }}/pip install
+    --timeout {{ repo_build_timeout }}
     --download {{ repo_build_output }}
     --no-binary :all:
     --constraint {{ repo_build_release_path }}/requirements_constraints.txt
@@ -61,7 +62,8 @@
 - name: Create OpenStack-Ansible requirement wheels
   shell: >-
     set -o pipefail;
-    pip wheel --timeout {{ repo_build_timeout }}
+    {{ repo_build_bin }}/pip wheel
+    --timeout {{ repo_build_timeout }}
     --wheel-dir {{ repo_build_output }}
     --find-links {{ repo_build_global_links_path }}
     --find-links {{ repo_build_output }}