[Fixes #10615] Implement fallback language for PyCSW to avoid warnings

[marthamareal]

References #10615

Checklist

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[giohappy]

@marthamareal I think you have to use black to fix some formatting. Look at the failing tests.

[codecov]

Codecov Report

Merging #10692 (3be1a98) into master (f360b63) will increase coverage by 0.00%.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #10692   +/-   ##
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  Coverage   62.14%   62.14%           
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  Files         828      828           
  Lines       51212    51212           
  Branches     6555     6555           
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+ Hits        31826    31828    +2     
+ Misses      17702    17699    -3     
- Partials     1684     1685    +1