fix deprecation warnings in tests (#82)

* stub

* update tests

* use util func

* add fallback for older versions

* don't test 3.6

.github/workflows/test_and_deploy.yml

@@ -70,9 +70,6 @@ jobs:
           - python-version: 3.8
             platform: ubuntu-18.04
             backend: pyside2
-          - python-version: 3.6
-            platform: windows-2016
-            backend: pyqt5
 
           # legacy Qt
           - python-version: 3.7