Fix UsePythonVersion warning

[dpwatrous]

Using 3.9.x generated a spurious warning about not specifying an exact Python version

[dpwatrous]

The warning in question:

[codecov]

Codecov Report

Merging #2559 (068a1f1) into master (bba20d0) will not change coverage.
The diff coverage is n/a.

❗ Current head 068a1f1 differs from pull request most recent head 16837e3. Consider uploading reports for the commit 16837e3 to get more accurate results

@@           Coverage Diff           @@
##           master    #2559   +/-   ##
=======================================
  Coverage   65.00%   65.00%           
=======================================
  Files         915      915           
  Lines       26366    26366           
  Branches     5190     5190           
=======================================
  Hits        17139    17139           
  Misses       9227     9227           

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