ci.github: fix codecov uploads

- switch to codecov action to enable tokenless uploads
- force coverage report output format
- remove codecov from dev-requirements

.github/workflows/main.yml

@@ -35,15 +35,13 @@ jobs:
         run: bash ./script/install-dependencies.sh
       - name: Test
         continue-on-error: ${{ matrix.continue }}
-        run: pytest -r a --cov
+        run: pytest -r a --cov --cov-report=xml
       - name: Lint
         continue-on-error: ${{ matrix.continue }}
         run: flake8
       - name: Upload coverage data
         continue-on-error: ${{ matrix.continue }}
-        env:
-          CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}
-        run: codecov
+        uses: codecov/codecov-action@v1
 
   documentation:
     name: Test docs

dev-requirements.txt

@@ -1,7 +1,6 @@
 pip>=6
 pytest
 pytest-cov
-codecov
 coverage
 mock
 requests-mock