small fixes to Python schema and tweak generators

[jll63]

• Remove xsdata[cli] from Python pip requirements file, because it requires ruff and then in turn Rust.
• Changes to schemagen:
  • If xsdata is not available, require user to install it manually.
  • Add copyright notice to generated files.
  • black-format the generated files.
• tweakgen: add copyright notice to generated file, and black-format it.

[678098]

@jll63 we can merge this PR to fix python UTs #411
There are also issues with quotes in the schemagen script

[678098]

@jll63 Need to also manually install black in CI

[jll63]

@jll63 Need to also manually install black in CI

I added black to requirements.txt. But I am not certain this is right. On one hand black is just like xsdata[cli] - it is needed by the two generators only. On the other hand, it does not pull heavy dependencies like xsdata[cli] does.

If we decide to not put black in the requirements, then I will have to make the two generators whine if it is not found, like schemagen also does with xsdata. Let's think about it over the weekend.