Fix coveralls integration

.github/workflows/python.yml

@@ -3,10 +3,11 @@ name: Python package
 on: [push]
 
 jobs:
-  build:
+  test:
 
     runs-on: ubuntu-latest
     strategy:
+      fail-fast: false
       matrix:
         python-version: [3.5, 3.7, 3.8]
 
@@ -27,4 +28,23 @@ jobs:
     - name: Test with unittest
       run: |
         coverage run --source=stcgal setup.py test
-        coveralls
+    - name: Coveralls
+      run: |
+        coveralls
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        COVERALLS_FLAG_NAME: ${{ matrix.python-version }}
+        COVERALLS_PARALLEL: true
+
+  coveralls:
+    name: Finish Coveralls
+    needs: test
+    runs-on: ubuntu-latest
+    container: python:3-slim
+    steps:
+    - name: Finished
+      run: |
+        pip3 install --upgrade coveralls
+        coveralls --finish
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}