• Closes add python 3.9 to ci configuration #1102
• I am familiar with the contributing guidelines
• [ ] Tests added
• [ ] Updates entries to docs/sphinx/source/api.rst for API changes.
• Adds description and name entries in the appropriate "what's new" file in docs/sphinx/source/whatsnew for all changes. Includes link to the GitHub Issue with :issue:`num` or this Pull Request with :pull:`num`. Includes contributor name and/or GitHub username (link with :ghuser:`user`).
• [ ] New code is fully documented. Includes numpydoc compliant docstrings, examples, and comments where necessary.
• Pull request is nearly complete and ready for detailed review.
• Maintainer: Appropriate GitHub Labels and Milestone are assigned to the Pull Request and linked Issue.

All of the base functionality works. Optional functionality that does not work:

• The forecast.py code needs netcdf4. As of now, netcdf4 needs a different build of numpy than would otherwise be pulled by the environment solver. This build of numpy spits out an ImportError on my mac.
• Numba is not yet compatible with 3.9.
• pysam installation issue on windows. Maybe related to Pip install causing "SAMNIDIR" error NatLabRockies/pysam#56. The easiest way to deal with this is to comment out the pysam line in the environment file and thus skip it on all platforms. That's my preference.