Only replace python when re-initializing the venv

We reinitialize the venv to ensure that the right version of
python is in the venv, but we do not want virtualenv to also
replace pip, setuptools and wheel so we tell it not to. If we
don't do this then virtualenv will install the latest available
version, which is not what we want.

Change-Id: Iad3ed2fbc9840305498fa2dfffdcb39043b9abe8
Partial-Bug: #1764470

tasks/python_venv_install.yml

@@ -64,10 +64,21 @@
   notify:
     - venv changed
 
+# NOTE(odyssey4me):
+# We reinitialize the venv to ensure that the right
+# version of python is in the venv, but we do not
+# want virtualenv to also replace pip, setuptools
+# and wheel so we tell it not to.
+# We do not use --always-copy for CentOS/SuSE due
+# to https://github.com/pypa/virtualenv/issues/565
 - name: Update virtualenv python and paths
   shell: |
     sed -si '1s/^.*python.*$/#!{{ (venv_destination_path ~ '/bin') | replace ('/','\/') }}\/python/' {{ venv_destination_path }}/bin/*
-    virtualenv {{ venv_destination_path }}
+    virtualenv {{ venv_destination_path }} \
+        {{ (ansible_pkg_mgr == 'apt') | ternary('--always-copy', '') }} \
+        --no-pip \
+        --no-setuptools \
+        --no-wheel
   args:
     executable: /bin/bash
     warn: no