>>> ImportError(spam='spam')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: ImportError does not take keyword arguments

However, it *does* take keyword arguments:

>>> ImportError(name='spam', path='spam')
ImportError()

Here's a patch with a simple test case.

Thanks for the review, Eric. Here's a new patch.

Looks good to me. Thanks for doing this. If no one objects in the meantime, I'll commit this in a few days.

Eric, do you want me to commit the patch? Should this also be committed to the 3.4 branch?

Here's a new patch which uses assertRaisesRegex instead of assertRaises.

The standard error message for this case is:

xxx() got an unexpected keyword argument 'foo'

I have no idea where that gets generated (a grep didn't teach me anything useful), but I think it would make sense to use that form for the message.

I think the fix can be applied to 3.4.

Thanks for the review, David.

The standard error message for this case is:

xxx() got an unexpected keyword argument 'foo'

I found two similar messages in the codebase:

• In Modules/itertoolsmodule.c:

  PyErr_SetString(PyExc_TypeError,
  "zip_longest() got an unexpected keyword argument");

• In Python/ceval.c:

  PyErr_Format(PyExc_TypeError,
  "%U() got an unexpected "
  "keyword argument '%S'",
  co->co_name,
  keyword);

But, in ImportError case it can take more than one keyword arguments:

   ImportError(spam="SPAM", eggs=True)

What error message should be printed for the above case?

Just the first unexpected keyword. That's what happens if you pass more than one unexpected keyword to a python function.

Assigning to Berker to apply his own patch since Eric has not gotten around to this.

Why not use PyArg_ParseTupleAndKeywords()?

I am a little uncomfortable with the empty tuple. It's only used as a placeholder for PyArg_ParseTupleAndKeywords. But this way we can achieve consistent error message. Don't know how to choose.

Ping.

Serhiy's patch looks good to me. It would be nice to add a test for multiple invalid keyword arguments:

    with self.assertRaisesRegex(TypeError, msg):
        ImportError('test', invalid='keyword', another=True)

Using empty_tuple seems reasonable to me. Brett and Eric, what do you think?

Left a review, but basically LGTM.

New changeset 9b8f0db1944f by Serhiy Storchaka in branch '3.5':
Issue bpo-21578: Fixed misleading error message when ImportError called with
https://hg.python.org/cpython/rev/9b8f0db1944f

New changeset 95549f4970d0 by Serhiy Storchaka in branch '3.6':
Issue bpo-21578: Fixed misleading error message when ImportError called with
https://hg.python.org/cpython/rev/95549f4970d0

New changeset 59268ac85f4e by Serhiy Storchaka in branch 'default':
Issue bpo-21578: Fixed misleading error message when ImportError called with
https://hg.python.org/cpython/rev/59268ac85f4e

Added a test for multiple invalid keyword arguments, added braces, fixed a leak.

But there is other oddity in ImportError constructor (bpo-28289).