Fix small float formatting

[OceanNuclear]

Fixed the edge case of having super-small (but non-zero) AffineFunc expressed as str.

• Closes ZeroDivisionError when getting the __repr__ if nominal value is too small #135
• Executed pre-commit run --all-files with no errors
• The change is fully covered by automated unit tests
• Documented in docs/ as appropriate
• Added an entry to the CHANGES file

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.55%. Comparing base (1975a4d) to head (90e811e).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #290      +/-   ##
==========================================
- Coverage   96.55%   96.55%   -0.01%     
==========================================
  Files          17       17              
  Lines        1947     1946       -1     
==========================================
- Hits         1880     1879       -1     
  Misses         67       67              

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macos-latest-3.11	95.01% <100.00%> (-0.01%)	⬇️
macos-latest-3.12	95.01% <100.00%> (-0.01%)	⬇️
macos-latest-3.8	95.00% <100.00%> (-0.01%)	⬇️
macos-latest-3.9	95.00% <100.00%> (-0.01%)	⬇️
no-numpy	75.12% <100.00%> (-0.02%)	⬇️
ubuntu-latest-3.10	95.01% <100.00%> (-0.01%)	⬇️
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windows-latest-3.11	95.01% <100.00%> (-0.01%)	⬇️
windows-latest-3.12	95.01% <100.00%> (-0.01%)	⬇️
windows-latest-3.8	95.00% <100.00%> (-0.01%)	⬇️
windows-latest-3.9	95.00% <100.00%> (-0.01%)	⬇️

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[codspeed-hq]

CodSpeed Performance Report

Merging #290 will not alter performance

_{Comparing OceanNuclear:fix-small_float_formatting (90e811e) with master (1975a4d)}

Summary

✅ 5 untouched benchmarks

[newville]

Thanks @OceanNuclear, I think this is all okay.
I will also say that UFloats with a stderr of zero (or less that 2e-16*nominal_value) basically make no sense and will likely cause problems. A value with a (finite) uncertainty can be represented as a UFloat. A value with an infinitesimal uncertainty is a Float. I find it odd how much attention UFloats with stderr=0 get.
I will also say that all of the formatting code in uncertainties is a distraction from the main point of the library.

And yet, I'll go with a bit of a shrug and hearty thanks @OceanNuclear for the fix to this very warty part of the code.

[newville]

@OceanNuclear merging... thanks!

[OceanNuclear]

Glad to be of help!