fix: improve error handling in image validation

[nijel]

• use contenxt to work with the file
• use targettet exceptions instead of wide Exception

[argos-ci]

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Build	Status	Details	Updated (UTC)
default (Inspect)	✅ No changes detected	-	May 23, 2026, 12:01 PM

[Copilot]

Pull request overview

Refactors validate_bitmap in weblate_web/models.py to use targeted Pillow exceptions instead of a broad except Exception, manages the opened image via a with block instead of try/finally, and adds a new BitmapValidationTest class covering valid PNGs, corrupted/invalid bytes, decompression-bomb headers, unsupported MIME types, and bad dimensions.

Changes:

• Introduce a PILLOW_VALIDATION_ERRORS tuple (OSError, SyntaxError, ValueError, DecompressionBombError) and use it for the open/verify calls, removing the broad except Exception and the sys.exc_info() traceback dance.
• Use with image: to ensure the image is closed, replacing the try/finally: image.close().
• Add BitmapValidationTest in weblate_web/tests.py with helpers to generate and corrupt PNGs and tests for the success and error paths of validate_bitmap.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
weblate_web/models.py	Narrows exception handling in validate_bitmap and switches to a context-managed image.
weblate_web/tests.py	Adds BitmapValidationTest covering valid, invalid, corrupt, oversized, unsupported, and mis-sized images.

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[codecov]

Codecov Report

❌ Patch coverage is 94.73684% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.52%. Comparing base (3a6a598) to head (859b941).
⚠️ Report is 14 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3832      +/-   ##
==========================================
+ Coverage   88.33%   88.52%   +0.18%     
==========================================
  Files          68       68              
  Lines        9507     9576      +69     
  Branches      821      824       +3     
==========================================
+ Hits         8398     8477      +79     
+ Misses        836      820      -16     
- Partials      273      279       +6     

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