Fix function inspection of functools.partials in migration files

[casparwylie]

Django migrations seem to include the use of functools.partial, though such objects do not carry the __name__ property, hence the errors

AttributeError: 'functools.partial' object has no attribute '__name__'

when running the linter on migrations that use functools.partial.

and for source code inspection...

n_linter.py", line 545, in get_runpython_model_import_issues
    source_code = inspect.getsource(code)
                  ^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/inspect.py", line 1270, in getsource
    lines, lnum = getsourcelines(object)
                  ^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/inspect.py", line 1252, in getsourcelines
    lines, lnum = findsource(object)
                  ^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/inspect.py", line 1063, in findsource
    file = getsourcefile(object)
           ^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/inspect.py", line 940, in getsourcefile
    filename = getfile(object)
               ^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/inspect.py", line 920, in getfile
    raise TypeError('module, class, method, function, traceback, frame, or '
TypeError: module, class, method, function, traceback, frame, or code object was expected, got partial

[David-Wobrock]

Hey @casparwylie 👋

Thanks for taking interest in the project, and taking the time to submit a PR!

Would you mind sharing an example of a data migration (RunPython) that is a partial function? :) I'm curious about the use case, and it will help us writing a test case for this logic.

Cheers!

[casparwylie]

No problem! So I've seen it around in some old migration code, and actually don't have much context myself, however I found this online as an example https://code.djangoproject.com/ticket/26475.

[codecov-commenter]

Codecov Report

Patch coverage: 96.42% and project coverage change: +0.01 🎉

Comparison is base (97a1f5c) 93.95% compared to head (6ba6102) 93.97%.

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #247      +/-   ##
==========================================
+ Coverage   93.95%   93.97%   +0.01%     
==========================================
  Files          77       78       +1     
  Lines        1969     1992      +23     
==========================================
+ Hits         1850     1872      +22     
- Misses        119      120       +1     

Impacted Files	Coverage Δ
...ata_migrations/migrations/0004_partial_function.py	90.00% <90.00%> (ø)
django_migration_linter/migration_linter.py	85.45% <100.00%> (+0.30%)	⬆️
tests/functional/test_data_migrations.py	79.34% <100.00%> (+0.57%)	⬆️

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