contrib: add a script for adding vendored type stubs to typeshed I really hate this, but pytype doesn't support PEP 561 and doesn't seem to have the equivalent of `MYPYPATH` to point to custom stubs. Ignoring the vendored stubs isn't necessarily harmful, but pytype has been choking on the vendored attr package after pytype 2022.03.29 with errors like this: File "/mnt/c/Users/Matt/hg/mercurial/linelog.py", line 52, in __iter__: Built-in function iter was called with the wrong arguments [wrong-arg-types] Expected: (collection: bytearray) Actually passed: (collection: mercurial.thirdparty.attr._make._CountingAttr) File "/mnt/c/Users/Matt/hg/mercurial/dirstateutils/v2.py", line 143, in pack: Built-in function len was called with the wrong arguments [wrong-arg-types] Expected: (obj: Sized) Actually passed: (obj: mercurial.thirdparty.attr._make._CountingAttr) Attributes of protocol Sized are not implemented on mercurial.thirdparty.attr._make._CountingAttr: __len__ File "/mnt/c/Users/Matt/hg/mercurial/dirstateutils/v2.py", line 144, in pack: No attribute 'rfind' on mercurial.thirdparty.attr._make._CountingAttr [attribute-error] File "/mnt/c/Users/Matt/hg/mercurial/dirstateutils/v2.py", line 146, in pack: Built-in function len was called with the wrong arguments [wrong-arg-types] Expected: (obj: Sized) Actually passed: (obj: mercurial.thirdparty.attr._make._CountingAttr) Attributes of protocol Sized are not implemented on mercurial.thirdparty.attr._make._CountingAttr: __len__ File "/mnt/c/Users/Matt/hg/mercurial/dirstateutils/v2.py", line 152, in pack: No attribute 'v2_data' on mercurial.thirdparty.attr._make._CountingAttr [attribute-error] File "/mnt/c/Users/Matt/hg/mercurial/util.py", line 2817, in go: unsupported operand type(s) for /: 'count: mercurial.thirdparty.attr._make._CountingAttr' and 'float: float' [unsupported-operands] No attribute '__truediv__' on 'count: mercurial.thirdparty.attr._make._CountingAttr' or '__rtruediv__' on 'float: float' Called from (traceback): line 2981, in __bytes__ This is essentially the same hack we've been using in TortoiseHg to add the vendored PyQt5 stubs. What I don't understand is pytype *still* generates *.pyi files under .pytype/pyi/mercurial/thirdparty/attr, even when the package is explicitly ignored in the pytype command line args. But it avoids the errors, which means we aren't stuck on pytype==2022.03.29. https://github.com/google/pytype/issues/151