module: support Python 3 only

.github/workflows/ci.yml

@@ -3,9 +3,9 @@ name: ci
 
 on:
   push:
-    branches: [master, three]
+    branches: [master]
   pull_request:
-    branches: [master, three]
+    branches: [master]
   workflow_dispatch:
   schedule:
   - cron: '37 4 * * 4'  # weekly on thursday morning
@@ -16,12 +16,8 @@ jobs:
     strategy:
       matrix:
         python-version:
-        - '2.7'
-        # Python 3.4 on GHA doesn't work due to fastdiff==0.2.0 failing with:
-        #   pkg_resources.DistributionNotFound: The 'setuptools_scm>=1.15.0' distribution was not found and is required by the application
-        #- '3.4'
-        - '3.5'
         - '3.7'
+        - '3.8'
         - '3.9'
     steps:
     - uses: actions/checkout@v2