testing Python 3.9

fixes #139
python/mypy#8614
https://github.com/python/mypy/releases
https://github.com/pre-commit/mirrors-mypy/releases

Author: PatMyron

.github/workflows/pr-ci.yml

@@ -16,7 +16,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python: [3.6, 3.7, 3.8]
+        python: [3.6, 3.7, 3.8, 3.9]
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python }}

.pre-commit-config.yaml

@@ -49,7 +49,7 @@ repos:
   - id: bandit
     files: ^(src|python)/
 - repo: https://github.com/pre-commit/mirrors-mypy
-  rev: v0.711
+  rev: v0.790
   hooks:
   - id: mypy
     files: ^src/