Bump PyO3 to 0.27

[tuxu]

Update pyo3 dependency to 0.27. Replace deprecated DowncastError with CastError.

[muhammad-fiaz]

Hello @tuxu i think this is related to the issue, i have encountered #97

[davidhewitt]

Thanks, very sorry for the delay 🙏

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 83.70%. Comparing base (bc3caf5) to head (f2b428e).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/error.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #96   +/-   ##
=======================================
  Coverage   83.70%   83.70%           
=======================================
  Files           3        3           
  Lines        1068     1068           
  Branches     1068     1068           
=======================================
  Hits          894      894           
  Misses        116      116           
  Partials       58       58           

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