fix: support python 3.7 and 3.8

3.9 is not supported yet due to av dep failures.

Author: Ivelin Ivanov

.github/workflows/pythonpackage.yml

@@ -10,7 +10,7 @@ jobs:
     strategy:
       max-parallel: 4
       matrix:
-        python-version: [3.7, 3.x]
+        python-version: [3.7, 3.8]
 
     steps:
     - uses: actions/checkout@v1