Goats 1378/show exception class when error message is empty

[miguelgomezgomez]

Checklist

• Added a release note in doc/changes using the PR number.

[codecov]

Codecov Report

❌ Patch coverage is 95.45455% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.32%. Comparing base (3522dd1) to head (9bd939e).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/goats_tom/tasks/download_goa_files.py	25.00%	3 Missing ⚠️
src/goats_tom/api_views/dataproduct_type.py	87.50%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #699      +/-   ##
==========================================
+ Coverage   85.25%   85.32%   +0.06%     
==========================================
  Files         334      336       +2     
  Lines       13704    13808     +104     
  Branches      729      734       +5     
==========================================
+ Hits        11684    11782      +98     
- Misses       1870     1875       +5     
- Partials      150      151       +1     

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