Estou executando o Python 2.7.6 em uma máquina Ubuntu. Quando eu corrotwill-sh (O Twill é um navegador usado para testar sites) no meu Terminal, estou obtendo o seguinte:

Traceback (most recent call last):
  File "dep.py", line 2, in <module>
    import twill.commands
  File "/usr/local/lib/python2.7/dist-packages/twill/__init__.py", line 52, in <module>
    from shell import TwillCommandLoop
  File "/usr/local/lib/python2.7/dist-packages/twill/shell.py", line 9, in <module>
    from twill import commands, parse, __version__
  File "/usr/local/lib/python2.7/dist-packages/twill/commands.py", line 75, in <module>
    browser = TwillBrowser()
  File "/usr/local/lib/python2.7/dist-packages/twill/browser.py", line 31, in __init__
    from requests.packages.urllib3 import connectionpool as cpl
ImportError: No module named packages.urllib3

No entanto, posso importar o urllib no console do Python. Qual seria a razão?