Hello,
I wanted to stay with the 2019 version of fenics, so I tried several builds of mshr 2019.1.0 available on conda-forge. The second newest build worked for me. I created a new Conda environment with
conda create -n fenicstest -c conda-forge mshr=2019.1.0=py38h2af9582_2
(the correct version of fenics is installed automatically because of dependencies) and in this environment the ImportError disappeared.
The build id py38h2af9582_2 above is for the macOS version, you can get the build ids of all available builds for your system via:
conda search mshr -c conda-forge
Maybe this works for you too…
Best regards
Martin