disable unavailable python 3.4 in CI, add 3.9

Author: Ivan Dlugos

.github/workflows/test.yaml

@@ -2,21 +2,14 @@
 # For more information see: https://help.github.com/actions/language-and-framework-guides/using-python-with-github-actions
 
 name: Test
-on: [ push, pull_request ]
+on: [push, pull_request]
 
 jobs:
   test:
     strategy:
       matrix:
-        os: [ ubuntu, windows, macos ]
-        python: [ 3.4, 3.5, 3.6, 3.7, 3.8 ]
-
-        # Python v3.4 is not available on macos and windows
-        exclude:
-          - os: macos
-            python: 3.4
-          - os: windows
-            python: 3.4
+        os: [ubuntu, windows, macos]
+        python: [3.5, 3.6, 3.7, 3.8, 3.9]
 
     runs-on: ${{ matrix.os }}-latest
 
@@ -34,4 +27,4 @@ jobs:
           pip install virtualenv
 
       - run: make depend
-      - run: make test
+      - run: make test