3.8.9

This bugfix release includes the following fixes and features:

• Bumping the psutil dependency requirement to psutil>=5.6.6 to
  address a double-free vulnerability documented in CVE-2019-18874.
• Adding a GitHub Actions workflow for building python wheels for Mac
  and Windows as well as a source distribution.
• Updating links in setup.py, README.rst and README_PYTHON.rst
  to refer to the repository's new home on github.
• Binary builds for Windows and Mac OS X have been moved to GitHub
  Actions from AppVeyor. All AppVeyor-specific configuration has been
  removed.
• Fixing an issue with the InVEST Makefile where make deploy was
  attempting to synchronize nonexistent sample data zipfiles with a
  storage bucket on GCP. Sample data zipfiles are only built on
  Windows, and so make deploy will only attempt to upload them when
  running on Windows.
• Fixed a bug in CLI logging where logfiles created by the CLI were
  incompatible with the natcap.invest.datastack operation that
  allows the UI to load model arguments from logfiles.
• Added error-handling in Urban Flood Risk Mitigation to tell users to
  "Check that the Soil Group raster does not contain values other than
  (1, 2, 3, 4)" when a ValueError is raised from _lu_to_cn_op.
• Updated the Makefile to use the new git location of the InVEST
  User's Guide repository at
  https://github.com/natcap/invest.users-guide
• Automated tests are now configured to use Github Actions for 32- and
  64-bit build targets for Python 3.6 and 3.7 on Windows. We are still
  using AppVeyor for our binary builds for the time being.
• Makefile has been updated to fetch the version string from git
  rather than hg. A mercurial client is still needed in order to
  clone the InVEST User's Guide.
• Removing Python 2 compatibility code such as future, pyqt4,
  basestring, unicode, six, unicode casting, etc...
• Update api-docs conf file to mock sdr.sdr_core and to use updated
  unittest mock