pypy3 cannot work as 'codecs.h' is needed (see python/typed_ast#97)

Author: SamuelMarks

.github/workflows/main.yml

@@ -7,7 +7,7 @@ jobs:
         runs-on: ubuntu-latest
         strategy:
             matrix:
-                python-version: [3.6, 3.7, 3.8, 3.9.0-beta.5, pypy3]
+                python-version: [3.6, 3.7, 3.8, 3.9.0-beta.5]
 
         steps:
             -   uses: actions/checkout@v2