title: `pip help install` raise UnicodeDecodeError
body: <p>When I tried to use pip to install Cython, I found that an error occurred while compiling. And some basic pip command also gave the same result: <code>UnicodeDecodeError</code>.    </p>
  
  <p>The error messages are all like this:</p>
  
  <pre><code>─➤  pip help install
  Exception:
  Traceback (most recent call last):
    File "/usr/local/lib/python2.6/dist-packages/pip/basecommand.py", line 126, in main
      self.run(options, args)
    File "/usr/local/lib/python2.6/dist-packages/pip/commands/help.py", line 19, in run
      command.parser.print_help()
    File "/usr/lib/python2.6/optparse.py", line 1664, in print_help 
      file.write(self.format_help().encode(encoding, "replace"))
  UnicodeDecodeError: 'ascii' codec can't decode byte 0xe4 in position 2964: ordinal not in range(128)
  </code></pre>
  
  <p>I have successfully installed other packages by pip and I don't know why this occurs suddenly. Can anyone tell me how to fix this bug?   </p>
  
  <p>Thank you!</p>
  
  <p>Some info:
  pip 1.0.2 on Ubuntu 10.04</p>