>>> help(open)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.0/site.py", line 349, in __call__
    import pydoc
  File "/usr/local/lib/python3.0/pydoc.py", line 55, in <module>
    import sys, imp, os, re, inspect, __builtin__, pkgutil
  File "/usr/local/lib/python3.0/inspect.py", line 32, in <module>
    import sys, os, types, re, dis, imp, tokenize, linecache
  File "/usr/local/lib/python3.0/tokenize.py", line 101, in <module>
    re.compile, (Token, PseudoToken, Single3, Double3))
ImportError: No module named itertools