Issue 30149: inspect.signature() doesn't support partialmethod without explicit self parameter

>>> import functools, inspect
>>> class A:
...     f = functools.partialmethod((lambda self, x, y, *args: ...), 1)
... 
>>> inspect.signature(A.f)
<Signature (self, y, *args)>
>>> class A:
...     f = functools.partialmethod((lambda *args: ...), 1)
... 
>>> inspect.signature(A.f)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/serhiy/py/cpython/Lib/inspect.py", line 3007, in signature
    return Signature.from_callable(obj, follow_wrapped=follow_wrapped)
  File "/home/serhiy/py/cpython/Lib/inspect.py", line 2757, in from_callable
    follow_wrapper_chains=follow_wrapped)
  File "/home/serhiy/py/cpython/Lib/inspect.py", line 2227, in _signature_from_callable
    return sig.replace(parameters=new_params)
  File "/home/serhiy/py/cpython/Lib/inspect.py", line 2780, in replace
    return_annotation=return_annotation)
  File "/home/serhiy/py/cpython/Lib/inspect.py", line 2725, in __init__
    raise ValueError(msg)
ValueError: duplicate parameter name: 'args'

I submitted the PR for this issue.

New changeset 378d70642aa1c8de2a53ecb811927faf0388db2d by Yury Selivanov (Dong-hee Na) in branch 'master':
bpo-30149: Fix partialmethod without explicit self parameter (#1308)
https://github.com/python/cpython/commit/378d70642aa1c8de2a53ecb811927faf0388db2d

New changeset e45ea377b8d9ae23893d4587003c6d3e7f54b99a by Serhiy Storchaka (Dong-hee Na) in branch '3.6':
bpo-30149: Fix partialmethod without explicit self parameter (#1308) (#1662)
https://github.com/python/cpython/commit/e45ea377b8d9ae23893d4587003c6d3e7f54b99a

New changeset fb0825c2784f80689c4c00c3ede22958faaf512c by Serhiy Storchaka (Dong-hee Na) in branch '3.5':
bpo-30149: Fix partialmethod without explicit self parameter (#1308) (#1663)
https://github.com/python/cpython/commit/fb0825c2784f80689c4c00c3ede22958faaf512c