WIP: Do not merge -- Test on Python 3.10 beta 1

https://www.python.org/download/pre-releases/

Author: cclauss

Diff for: .github/workflows/build.yml

@@ -12,7 +12,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: actions/setup-python@v2
         with:
-          python-version: "3.9"
+          python-version: "3.10"
       - uses: actions/cache@v2
         with:
           path: ~/.cache/pip