Zuul runs tests in py36 only

Python 3.6 is the oldest version of python
supported by the package, and newer, supported,
minor versions do not break any substantial functionality
by design, while introducing new features.

Therefore we do not need to run unit tests for
each minor version. As all possible issues affecting
versions >3.6 would necessarily be related to features
introduced in versions >3.6.

Victoria test template was removed from .zuul.yaml.
The pep8 test environment was folded into linters in tox.ini.
Zuul is now explicitly running tests only in one, oldest supported,
python environment, Python 3.6.

PEP387: https://www.python.org/dev/peps/pep-0387/
https://docs.python.org/3/whatsnew/3.7.html#porting-to-python-37
https://docs.python.org/3/whatsnew/3.8.html#porting-to-python-3-8

Signed-off-by: Jiri Podivin <jpodivin@redhat.com>
Change-Id: Iec86be1b44a494c815ffff042b8693d7fc830b74

.zuul.yaml

@@ -18,9 +18,9 @@
 - project:
     templates:
       - check-requirements
-      - openstack-python3-victoria-jobs
     check:
       jobs:
+        - openstack-tox-py36
         - openstack-tox-linters
         - openstack-tox-cover
         - openstack-tox-docs: &tripleo-docs
@@ -31,6 +31,7 @@
         - validations-libs-functional
     gate:
       jobs:
+        - openstack-tox-py36
         - openstack-tox-linters
         - openstack-tox-docs: *tripleo-docs
         - validations-libs-functional

tox.ini

@@ -64,6 +64,7 @@ deps =
     -r {toxinidir}/requirements.txt
     -r {toxinidir}/test-requirements.txt
 commands =
+    {[testenv:pep8]commands}
     {[testenv:whitespace]commands}
     {[testenv:shebangs]commands}