Close files in create thumbnail

[satya-waylit]

Use contextlib.closing to close the orig file in Avatar.create_thumbnail method.

Fixes #244

[johanneswilm]

@satya-waylit Thanks for this. I see some tests failing. Do you know what this is about?

[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.60%. Comparing base (4955d2d) to head (73d1853).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
avatar/models.py	88.88%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #252      +/-   ##
==========================================
+ Coverage   64.34%   64.60%   +0.25%     
==========================================
  Files          21       21              
  Lines         906      907       +1     
==========================================
+ Hits          583      586       +3     
+ Misses        323      321       -2     

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[satya-waylit]

@johanneswilm Thanks for merging. Looks like you got the test failures