fix GH actions parsing 3.10 as a number.

Author: David Grant

.github/workflows/test.yml

@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-18.04
     strategy:
       matrix:
-        python-version: [2.7, 3.5, 3.6, 3.7, 3.8, 3.9, 3.10, pypy2, pypy3]
+        python-version: ['2.7', '3.5', '3.6', '3.7', '3.8', '3.9', '3.10', 'pypy2', 'pypy3']
 
     steps:
     - uses: actions/checkout@v2