我在Ubuntu机器上运行Python 2.7.6。当我twill-sh在终端中运行（Twill是用于测试网站的浏览器）时，得到以下信息：

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

但是，我可以在Python控制台中导入urllib。可能是什么原因？