mix_stderr parameter was removed from click 8.2.0

[MeggyCal]

From click 8.2.0 changelog:

Keep stdout and stderr streams independent in CliRunner. Always collect stderr output and never raise an exception. Add a new output stream to simulate what the user sees in its terminal. Removes the mix_stderr parameter in CliRunner. [:issue:`2522`](https://github.com/pallets/click/blob/main/CHANGES.rst#id27) [:pr:`2523`](https://github.com/pallets/click/blob/main/CHANGES.rst#id29)

so mix_stderr=False throws an error and is redundant.

[MeGaGiGaGon]

Thanks for the contribution!
I don't understand the point/default behavior for why mix_stderr=False, but wouldn't that regress while click 8.2.0 is still unreleased?

[cobaltt7]

Also, wouldn't this change make the entire class redundant?

[JelleZijlstra]

Yes, seems like we may have to make this conditional on Click version.

[MeggyCal]

Ok, I will try to make it conditional 🙂

[MeggyCal]

sorry, I couldn't think of a more pythonic way