Merge pull request #1319 from brosaplanella/fix-ci-01-21

Fix GitHub actions MacOS

Author: brosaplanella

.github/workflows/test_on_push.yml

@@ -47,11 +47,17 @@ jobs:
         sudo apt install gfortran gcc libopenblas-dev graphviz
         sudo apt install python${{ matrix.python-version }}.dev
     
+    # Added fixes to homebrew installs:
+    # rm -f /usr/local/bin/2to3 
+    # (see https://github.com/actions/virtual-environments/issues/2322)
+    # brew unlink gcc@8 gcc@9
+    # (see https://github.com/actions/virtual-environments/issues/2391)
     - name: Install MacOS system dependencies
       if: matrix.os == 'macos-latest'
       run: |
         rm -f /usr/local/bin/2to3
         brew update
+        brew unlink gcc@8 gcc@9
         brew install graphviz
         brew install openblas