[CI] Do not set ansible_python_interpreter for Zuul

Zuul 4.6.0 does not allow to set ansible_python_interpreter. [1]
Instead, with the current Zuul and Ansible, this should be
automatically set to the proper python.

This patch is required to restore the jobs which are ignored
otherwise. [2] [3]

Additionally, this change avoids the use of Ansible's pip
module because it tries to use setuptools from the
ansible_python_interpreter first even if another executable is
set.

[1] http://lists.openstack.org/pipermail/openstack-discuss/2021-June/023291.html
[2] http://lists.openstack.org/pipermail/openstack-discuss/2021-June/023326.html
[3] http://lists.openstack.org/pipermail/openstack-discuss/2021-June/023321.html

Change-Id: I53e666d59d0cce26e38c6f66a39eb204bda502d3

Author: yoctozepto

tests/run.yml

@@ -196,22 +196,20 @@
     # NOTE(mgoddard): We need a recent pip to install the latest cryptography
     # library. See https://github.com/pyca/cryptography/issues/5753
     - name: install pip 19.1.1+
-      pip:
-        name: "pip>=19.1.1"
-        executable: "pip3"
-        extra_args: "--user"
+      command: >-
+        python3 -m pip install --user
+        pip>=19.1.1
 
     - name: install kolla-ansible and dependencies
       vars:
         # Test latest ansible version on Ubuntu, minimum supported on others.
         ansible_version_constraint: "{{ '==2.9.*' if is_upgrade else '==2.10.*' }}"
-      pip:
-        name:
-          - "{{ kolla_ansible_src_dir }}"
-          - "ansible{{ ansible_version_constraint }}"
-          - "ara<1.0.0"
-        executable: "pip3"
-        extra_args: "-c {{ upper_constraints_file }} --user"
+      command: >-
+        python3 -m pip install --user
+        -c {{ upper_constraints_file }}
+        {{ kolla_ansible_src_dir }}
+        ansible{{ ansible_version_constraint }}
+        ara<1.0.0
 
     - name: get ARA callback plugin path
       command: "python3 -m ara.setup.callback_plugins"
@@ -539,10 +537,10 @@
           when: item.when | default(true)
 
         - name: upgrade kolla-ansible
-          pip:
-            name: "{{ kolla_ansible_src_dir }}"
-            executable: pip3
-            extra_args: "-c {{ upper_constraints_file }} --user"
+          command: >-
+            python3 -m pip install --user
+            -c {{ upper_constraints_file }}
+            {{ kolla_ansible_src_dir }}
 
         # Update passwords.yml to include any new passwords added in this
         # release.

zuul.d/base.yaml

@@ -41,9 +41,6 @@
       neutron_external_interface_name: "veth-{{ neutron_external_bridge_name }}-ext"
       neutron_external_vxlan_interface_name: vxlan1
       tls_enabled: false
-      # NOTE(yoctozepto): Ansible on Debian defaults to /usr/bin/python which is
-      # python2. Let's use python3 instead as expected in 2020 and beyond.
-      ansible_python_interpreter: python3
       configure_swap_size: 0
     roles:
       - zuul: zuul/zuul-jobs