In Python 2.6, attempting to import depecated modules in IDLE raises a
TypeError exception.  I verified this with sets, mimify, and MimeWriter.
 Here's the output for sets:

>>> import sets

Traceback (most recent call last):
  File "<pyshell#2>", line 1, in <module>
    import sets
  File "C:\Python26\Lib\sets.py", line 85, in <module>
    stacklevel=2)
  File "C:\Python26\Lib\warnings.py", line 29, in _show_warning
    file.write(formatwarning(message, category, filename, lineno, line))
TypeError: idle_formatwarning_subproc() takes exactly 4 arguments (5 given)

The other modules give a similar trace.

Normally, I wouldn't consider this a serious issue, but there are some
major packages out there that still use deprecated modules such as
these.  For example, MySQLdb 1.2.2 and SQLAlchemy 4.7p1 import the sets
module so they can't be used at all in IDLE.