stubs for xtea library

[rajohnson]

Adds stubs for the xtea encyption library.

I think that this is ready to review, unless CI catches something I've missed.

[hauntsaninja]

Note that stub_uploader is different from stubtest.

stub_uploader will not be happy with pep272_encryption as a requirement because of:
https://github.com/typeshed-internal/stub_uploader/blob/32dca63e0cdb13393454bde4ed76fefa72d99a4f/stub_uploader/metadata.py#L151-L163
I should write up an issue that's not on that PR, but see the link in code

[rajohnson]

@hauntsaninja My understanding is that pep272_encryption would have to be reviewed by the typeshed team and manually added to EXTERNAL_REQ_ALLOWLIST in stub_uploader/metadata.py in order for this to pass. Is this correct?

pep272_encryption is pretty obscure and was created by the author of the library that I'm trying to make stubs for. I'm not sure that it will be worth your time if my understanding is correct, is it worth continuing this pull request?

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[hauntsaninja]

Yeah, I think it would be a little challenging to add pep272_encryption to that allowlist. I wrote up typeshed-internal/stub_uploader#90 which has details of the exact situation.

Three alternative options are:

• Given that the author of xtea has type annotations on pep272_encryption, maybe they'd be willing to accept a PR adding annotations directly to xtea? In general, if types can be upstreamed that's preferable to having types in typeshed
• I'm not sure that this would work well here, but we could just include the API of PEP272Cipher in XTEACipher and have users of these stubs rely on substructural typing (Protocols)
• If you're willing to wait, maybe we can resolve some of the barriers that make us hesitant to add things to the allowlist in stub_uploader, as described in that issue

In all cases, we're very happy to review the stubs themselves and are grateful for your contribution of them! :-)

[rajohnson]

Ok, contributing the stubs to xtea makes a lot of sense, I'll pursue that option first. Thanks for your help!