User python interpreter prescribed by CI

[DonJayamanne]

For #4920

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• Title summarizes what is changing
• Has a news entry file (remember to thank yourself!)
• [n/a] Has sufficient logging.
• [n/a] Has telemetry for enhancements.
• [n/a] Unit tests & system/integration tests are added/updated
• [n/a] Test plan is updated as appropriate
• [n/a] package-lock.json has been regenerated by running npm install (if dependencies have changed)
• [n/a] The wiki is updated with any design decisions/details.

[codecov]

Codecov Report

Merging #4921 into master will increase coverage by 1%.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #4921   +/-   ##
======================================
+ Coverage      63%     63%   +1%     
======================================
  Files         372     372           
  Lines       14624   14625    +1     
  Branches     1159    1159           
======================================
+ Hits         9068    9069    +1     
  Misses       5348    5348           
  Partials      208     208