Anaconda GH Action Workaround

[jared321]

The anaconda GH action recently started failing for the macos-* test setups. It appears that while conda indicates that OpenMPI has been installed, the MPI wrappers are not in the PATH and I was not able to find the MPI installation where it was in the past.

I suspect that this is an issue with miniconda, conda, or the action that installs Miniconda.

For now, I revereted setup-miniconda to an older version that allows me to specify an older version of miniconda that works and in a way that is not specific to a particular OS/processor. With this, all anaconda tests are passing again.

I create this Issue to remind us to try using the "latest" miniconda version again in the future to see if the underlying issue has been resolved.