Increase stacklevel of timezone warning

[CodyCBakerPhD]

Motivation

I just ran across a confusing case during a conversion.

I'm setting both session_start_time and the subect's date_of_birth.

I intentionally set the tzinfo for the datetime of the session_start_time, but was very confused for while as to why I kept getting the warning from PyNWB about not having set a timezone.

Little did I know it was not coming from the session_start_time (which 90+% of the time is the cause of that warning), but it was from https://github.com/NeurodataWithoutBorders/pynwb/blob/dev/src/pynwb/file.py#L120 which does the same thing to the subject date_of_birth.

Using a higher stacklevel would have saved me a lot of time figuring this out, because it would have shown me a line in the traceback related to the field that was being parsed.

Checklist

• Did you update CHANGELOG.md with your changes?
• Have you checked our Contributing document?
• Have you ensured the PR clearly describes the problem and the solution?
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[codecov]

Codecov Report

Merging #1641 (c90ac00) into dev (494e288) will increase coverage by 0.11%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              dev    #1641      +/-   ##
==========================================
+ Coverage   91.32%   91.43%   +0.11%     
==========================================
  Files          25       25              
  Lines        2535     2535              
  Branches      481      481              
==========================================
+ Hits         2315     2318       +3     
+ Misses        139      137       -2     
+ Partials       81       80       -1     

Flag	Coverage Δ
integration	70.49% <0.00%> (ø)
unit	84.49% <100.00%> (+0.11%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/pynwb/file.py	88.77% <100.00%> (+0.74%)	⬆️

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[rly]

Although it is not that relevant to this PR, could you please add a test for _add_missing_timezone in this or another PR? There is apparently no coverage of that line.

[rly]

Otherwise, looks good to me. Thanks!