api_core: fix / disable the broken 'pytype' session in 'nox'.

[tseaver]

CI is broken for unrelated PRs due to this failure, e.g. see this Kokoro run for PR #7628.

[tseaver]

@rchen152 Is this new failure in our 'pytype' session due to a recent release of pytype, e.g. perhaps containing google/pytype#314?

[rchen152]

This looks like more fallout from python/typeshed@e45f443. Typeshed is representing the return value of functools.partial() as a function rather than a class in order to get better type-checking when the returned partial is used. I'll send a PR to silence the failure (should be as simple as adding # pytype: disable=wrong-arg-types at the end of the line that pytype is complaining about).

[tseaver]

@rchen152 That is an odd choice for Typeshed to make: functools.partial is most definitely a type in both Python 2.7 and 3.7:

$ python2.7
Python 2.7.14 (default, Oct  4 2017, 16:09:27) 
[GCC 4.8.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import functools
>>> functools.partial
<type 'functools.partial'>
>>> ^D
$ python3.7
Python 3.7.1 (default, Oct 22 2018, 11:31:38) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import functools
>>> functools.partial
<class 'functools.partial'>
>>> ^D

[rchen152]

I didn't author or review that change, but from what I understand, the reasoning was that it caused only a small number of false positives and made type-checking more precise in the vast majority of cases.