Drop unrelated Python versions (#963)

Python 3.5, 3.6, and 3.7 are no longer needed on this branch.

(cherry picked from commit 0fe0f01)

.github/workflows/tox.yaml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.5, 3.6, 3.7, 3.8, 3.9]
+        python-version: [3.8, 3.9]
 
     steps:
     - uses: actions/checkout@v1
@@ -24,4 +24,4 @@ jobs:
     - name: Lint with tox
       run: tox -e pep8
     - name: Test with tox
-      run: tox -e py${{ matrix.python-version }}
+      run: tox -e py${{ matrix.python-version }}

tox.ini

@@ -30,18 +30,6 @@ commands = nosetests --with-coverage --cover-package=zaza.openstack {posargs} {t
 basepython = python3
 deps = -r{toxinidir}/requirements.txt
 
-[testenv:py3.5]
-basepython = python3.5
-deps = -r{toxinidir}/requirements.txt
-
-[testenv:py3.6]
-basepython = python3.6
-deps = -r{toxinidir}/requirements.txt
-
-[testenv:py3.7]
-basepython = python3.7
-deps = -r{toxinidir}/requirements.txt
-
 [testenv:py3.8]
 basepython = python3.8
 deps = -r{toxinidir}/requirements.txt