Actions: Fix 422 error on Coveralls (PyMySQL#949)

* Actions: Update coveralls flag name
* fix 422 error

See TheKevJames/coveralls-python#252

Author: methane

.github/workflows/test.yaml

@@ -106,21 +106,23 @@ jobs:
           pytest -v --cov --cov-config .coveragerc tests/test_mariadb_auth.py
 
       - name: Report coverage
-        run: coveralls
+        run: coveralls --service=github
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          COVERALLS_FLAG_NAME: ${{ matrix.test-name }}
+          COVERALLS_FLAG_NAME: ${{ matrix.py }}-${{ matrix.db }}
           COVERALLS_PARALLEL: true
 
   coveralls:
     name: Finish coveralls
     runs-on: ubuntu-20.04
     needs: test
-    container: python:3-slim
     steps:
+    - uses: actions/setup-python@v2
+      with:
+        python-version: 3.9
     - name: Finished
       run: |
-        pip3 install --upgrade coveralls
-        coveralls --finish
+        pip install --upgrade coveralls
+        coveralls --finish --service=github
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}