Today's lesson: Never call your module types.py if you plan to run
Python from when standing in the same directory. It took me some
time to figure out what was going on:

$ touch types.py   # empty file
$ python
Traceback (most recent call last):
  File "/usr/lib/python2.7/site.py", line 68, in <module>
    import os
  File "/usr/lib/python2.7/os.py", line 398, in <module>
    import UserDict
  File "/usr/lib/python2.7/UserDict.py", line 83, in <module>
    import _abcoll
  File "/usr/lib/python2.7/_abcoll.py", line 70, in <module>
    Iterable.register(str)
  File "/usr/lib/python2.7/abc.py", line 107, in register
    if not isinstance(subclass, (type, types.ClassType)):
AttributeError: 'module' object has no attribute 'ClassType'

"Weeeaaht?"