Revert "Install python3.6 on ubuntu xenial for Tempest venv"

This reverts commit 0b596470c8.

To make clear we don't actually need it since neutron-lib
was properly pinned in u-c for py3.5.

Change-Id: I58619915dd1032f3a7202a78b193ed8c66dabd24
Depends-on: https://review.opendev.org/704688

lib/tempest

@@ -690,13 +690,6 @@ function install_tempest {
     pip_install 'tox!=2.8.0'
     pushd $TEMPEST_DIR
     tox -r --notest -efull
-    local ver
-    ver=$(tox -evenv-tempest -- python --version)
-    echo Python version installed in Tempest venv: $ver
-    if python3_enabled; then
-        ver=$(tox -evenv-tempest -- python3 --version)
-        echo Python3 version installed in Tempest venv: $ver
-    fi
     # NOTE(mtreinish) Respect constraints in the tempest full venv, things that
     # are using a tox job other than full will not be respecting constraints but
     # running pip install -U on tempest requirements

tools/fixup_stuff.sh

@@ -234,32 +234,10 @@ function fixup_virtualenv {
     fi
 }
 
-# Ubuntu Xenial with py3.6
-#-------------------------
-# Install py3.6 on Xenial for Tempest
-function fixup_tempest_on_xenial {
-    # All the stable branches are tested with Tempest and its plugins master
-    # branch. In ussuri cycle, openstack is dropping the py2.7 support which
-    # make Tempest & its plugin not able to run on py2.7 or sometime <py3.6
-    # venv for code or dependency version compatibility reason
-    # (Example: bug#1860033). Tempest is being installed and run on venv
-    # which give us flexibility to run with any interpreter irrespective of
-    # tested env python version. Stable branches till stable/rocky use
-    # ubuntu xenial which does not have py3.6 and so does need to be
-    # installed separately.
-    if [[ "$DISTRO" == "xenial" ]]; then
-        echo "Installing python 3.6 from ppa"
-        sudo add-apt-repository ppa:deadsnakes/ppa --yes
-        sudo apt-get update
-        sudo apt-get install python3.6 python3.6-dev --yes
-    fi
-}
-
 function fixup_all {
     fixup_keystone
     fixup_uca
     fixup_python_packages
     fixup_fedora
     fixup_virtualenv
-    fixup_tempest_on_xenial
 }