[issue15223] datetime instances lack __module__ attribute

New submission from Chris Jerdonek <chris.jerdonek <at> gmail.com>:

Instances of datetime.datetime don't seem to have the '__module__' attribute even though the datetime
class itself does.

This seems to contradict Section 3.2 of the Python documentation about the standard type hierarchy (in the
subsection called "Class instances"): http://docs.python.org/dev/reference/datamodel.html#the-standard-type-hierarchy

"A class instance has a namespace implemented as a dictionary which is the first place in which attribute
references are searched. When an attribute is not found there, and the instance’s class has an
attribute by that name, the search continues with the class attributes."

Instances of other classes defined in the standard library do have the attribute.

The session below illustrates the issue:

Python 3.3.0a4 (v3.3.0a4:7c51388a3aa7, May 30 2012, 16:58:42) 
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from datetime import datetime
>>> datetime.__module__
'datetime'
>>> d = datetime(2000, 1, 1)
>>> d.__class__ 
<class 'datetime.datetime'>
>>> d.__module__
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'datetime.datetime' object has no attribute '__module__'