message: Use set up homebrew action to update homebrew:
  The goal is not to rely on bintray anymore, since end of service is schedule for May 1st 2021.
  https://github.com/Homebrew/discussions/discussions/691\#discussioncomment-600559
diff: @@ -81,6 +81,10 @@ jobs:
  sudo apt-get install mpich libmpich-dev
  export MAKE_CXX_FLAG="MPICXX=mpic++"
  + - name: Set up Homebrew
  + if: matrix.mpi == 'parallel' && matrix.os == 'macos-10.15'
  + uses: Homebrew/actions/setup-homebrew@master
  +
  - name: get MPI (MacOS)
  if: matrix.mpi == 'parallel' && matrix.os == 'macos-10.15'
  run: |
  