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The TypeError message when a call to subprocess.Popen() lacks the args argument is incorrect.
For 3.3 and 3.4, the message incorrectly says that a positional argument is required when a keyword argument will do:
>>> import subprocess
>>> subprocess.Popen()
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: __init__() missing 1 required positional argument: 'args'
>>> subprocess.Popen(args=['test'])
<subprocess.Popen object at 0x10bed4840>
For 3.2 and 2.7, the problem is slightly different. It says that two arguments are needed and that two have been given:
>>> subprocess.Popen()
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: __init__() takes at least 2 arguments (1 given)
>>> subprocess.Popen(shell=True)
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: __init__() takes at least 2 arguments (2 given)
I don't know if this issue affects other functions in the standard library, but I suspect it might.

I don't think the first part of the report has anything to do with subprocess.Popen:
>>> def f(x):
... return
... 
>>> f()
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
TypeError: f() missing 1 required positional argument: 'x'
See the related discussion starting at:
http://mail.python.org/pipermail/python-dev/2012-September/121760.html 

Also see the terminology-related issue 15990 created from that thread.

By the way, I think this message from Nick is the closest to a resolution from that thread:
"We've already had this terminology discussion and documented the results in PEP 362. The rest of the docs may require updates to be brought in line with that."
(http://mail.python.org/pipermail/python-dev/2012-September/121791.html)

> TypeError: __init__() missing 1 required positional argument: 'args'
I think something like the following would be more correct:
__init__() missing argument for parameter 'args'

I think changing the message will break a lot of tests.
Here are some examples just from CPython:
https://github.com/python/cpython/blob/master/Lib/test/test_dataclasses.py#L2655
https://github.com/python/cpython/blob/master/Lib/test/test_extcall.py
It would also outdate some documentation examples.