Option to error on missing Jinja2 variables

[DavidHuber-NOAA]

Description

This allows a user to specify if they want to allow missing variables in a jinja2 template. If allow_missing == False, a NameError will be raised with the name of the variable that is undefined. The default is True, which is the current behavior.

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

• pynorms
• pytests

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes need updates to the documentation. I have made corresponding changes to the documentation
• My changes generate no new warnings
• New and existing tests pass with my changes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 47.93%. Comparing base (71f6b10) to head (df2875c).
Report is 9 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #27      +/-   ##
===========================================
+ Coverage    47.87%   47.93%   +0.06%     
===========================================
  Files           18       18              
  Lines         1650     1650              
  Branches       335      335              
===========================================
+ Hits           790      791       +1     
+ Misses         801      799       -2     
- Partials        59       60       +1     

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[aerorahul]

looks good.
Thanks for adding a test!