Change CI pytest-cov and coverage versions to fix UnicodeDecodeError.…

… All branches now trigger CI

.github/workflows/ci.yml

@@ -2,11 +2,7 @@
 
 name: Continuous Integration
 
-on:
-  push:
-    branches: [ master ]
-  pull_request:
-    branches: [ master ]
+on: [push, pull_request]
 
 jobs:
   build:
@@ -28,7 +24,7 @@ jobs:
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip
-        python -m pip install flake8 pytest pytest-cov
+        python -m pip install flake8 pytest pytest-cov==2.10.1 coverage==4.5.4
         if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
     - name: Install PyMatching
       run: |