Added try-catch for autodoc mock-import

[RobertoRoos]

Resolving #82 (again...)

This is the suggestion of @lucc , posted here: #82 (comment)

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 50.11%. Comparing base (de7c367) to head (88cd1f0).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sphinxarg/ext.py	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #89      +/-   ##
==========================================
- Coverage   50.15%   50.11%   -0.04%     
==========================================
  Files          18       18              
  Lines        1288     1291       +3     
  Branches      262      263       +1     
==========================================
+ Hits          646      647       +1     
- Misses        598      599       +1     
- Partials       44       45       +1     

Flag	Coverage Δ
unittests	49.88% <33.33%> (-0.04%)	⬇️

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[RobertoRoos]

Hm, I'm a little in doubt now. I feel the intended method to import is the short version:

from sphinx.ext.autodoc import mock

So maybe we should prioritize that one. If for no other reason then to prevent us being the cause of an import error for the next package.

EDIT: I changed it but let's see what the bosses say over at sphinx-doc/sphinx#14333