Also pin pip/setuptools when creating Xenial venvs

We still have some Ubuntu Xenial servers, so cap the max usable pip
and setuptools versions in their venvs like we already do for
Bionic, in order to avoid broken installations. Switch our
conditionals from release name comparisons to version numbers in
order to more cleanly support ranges. Also make sure the borg run
test is triggered by changes to the create-venv role.

Change-Id: I5dd064c37786c47099bf2da66b907facb517c92a

playbooks/roles/create-venv/tasks/main.yaml

@@ -2,10 +2,22 @@
   assert:
     that: create_venv_path is defined
 
+# Xenial's default pip will try to pull in packages that
+# aren't compatible with 3.5.  Cap them
+- name: Setup bionic era venv
+  when: ansible_distribution_version is version('16.04', '==')
+  pip:
+    name:
+      - pip<21
+      - setuptools<51
+    state: latest
+    virtualenv: '{{ create_venv_path }}'
+    virtualenv_command: '/usr/bin/python3 -m venv'
+
 # Bionic's default pip will try to pull in packages that
 # aren't compatible with 3.6.  Cap them
 - name: Setup bionic era venv
-  when: ansible_distribution_release == 'bionic'
+  when: ansible_distribution_version is version('18.04', '==')
   pip:
     name:
       - pip<22
@@ -15,7 +27,7 @@
     virtualenv_command: '/usr/bin/python3 -m venv'
 
 - name: Setup later era venv
-  when: ansible_distribution_release != 'bionic'
+  when: ansible_distribution_version is version('20.04', '>=')
   pip:
     name:
       - pip

zuul.d/system-config-run.yaml

@@ -392,6 +392,7 @@
       - playbooks/bootstrap-bridge.yaml
       - playbooks/roles/install-borg
       - playbooks/roles/borg-backup
+      - playbooks/roles/create-venv
       - playbooks/zuul/templates/host_vars/borg-backup
       - testinfra/test_borg_backups.py
     host-vars: