virtualenv-config : add download for virtualenv seeder

As described in the inline comments, this is working around a broken
version of setuptools vendored by virtualenv currently.  Specify in a
config file that it should download the latest helper tools, rather
then rely on the inbuilt versions.

Add to the base-test pre-playbook; after testing we can move to the
base playbook.

Change-Id: Ib17017637eae81a3ff57302e7c77945f2045b5ac

playbooks/base-test/pre.yaml

@@ -34,3 +34,7 @@
     - mirror-info
     - role: configure-mirrors
       set_apt_mirrors_trusted: True
+    # NOTE(ianw): 2020-03-27 : broken setuptools, until
+    #  https://github.com/pypa/virtualenv/issues/1752
+    # releases
+    - virtualenv-config

roles/virtualenv-config/README.rst

@@ -0,0 +1,11 @@
+Write a configuration file for virtualenv
+
+Generally we do not require any specific virtualenv configuration.
+However, there are corner cases; such as virtualenv shipping an
+vendored version of setuptools that needs to be ignored or similar.
+
+The exact action this role is taking may depend on any issues it is
+working around.  See comments inline.
+
+** Role Variables **
+

roles/virtualenv-config/tasks/main.yaml

@@ -0,0 +1,19 @@
+- name: Set config file
+  set_fact:
+    virtualenv_config_file: '{{ ansible_env.HOME }}/.config/virtualenv/virtualenv.ini'
+
+- name: Ensure config directory
+  file:
+    path: '{{ virtualenv_config_file | dirname }}'
+    state: directory
+    mode: 0755
+
+# NOTE(ianw) : 2020-03-27 workaround 46.1.1 broken setuptools
+#  https://github.com/pypa/virtualenv/issues/1752
+- name: Add download flag, to not use vendorded versions of setuptools/pip
+  ini_file:
+    path: '{{ virtualenv_config_file }}'
+    section: 'virtualenv'
+    option: download
+    value: 'True'
+    mode: '0644'