stop allowing extra positional args in arg parser

[li-roy]

Arg parser allowed additional positional args to be parsed into keyword-only params.

Fixes a couple cases:

• The positional argument happens to be of the right type, and it just works silently. Now, we fail as expected.
• The positional argument fails later down the line. Now, we fail at the appropriate time and get a better error message.

Pre-fix:

>>> torch.cuda.LongTensor((6, 0), 1, 1, 0)
tensor([6, 0], device='cuda:1')

Post-fix:

>>> torch.cuda.LongTensor((6, 0), 1, 1, 0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: new() received an invalid combination of arguments - got (tuple, int, int, int), but expected one of:
 * (torch.device device)
 * (torch.Storage storage)
 * (Tensor other)
 * (tuple of ints size, torch.device device)
 * (object data, torch.device device)

Pre-fix:

>>> a = torch.tensor(5)
>>> a.new_zeros((5,5), 0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: new_zeros(): argument 'dtype' (position 2) must be torch.dtype, not int

Post-fix:

>>> a = torch.tensor(5)
>>> a.new_zeros((5,5), 0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: new_zeros() takes 1 positional argument but 2 were given

fixes #8351

[ezyang]

Tests?

(Also, I feel like the error messages could be improved more, but that can be for a later patch.)

[ailzhang]

cc: @li-roy

[fmassa]

ping @li-roy about Ed's comment on tests.

[zou3519]

This is pretty hi-pri. I'll give it a review after you update it @li-roy

Related: #11427

[li-roy]

@pytorchbot retest this please

[zou3519]

LGTM. Let me know what the error message looks like though (a self.assertRaisesRegex would be great)

[li-roy]

@pytorchbot retest this please

[facebook-github-bot]

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