title: how to pip install with proxy
body: <p>I tried this command </p>
  
  <pre><code>pip install --proxy="username:password@192.168.1.1:3128" packagename
  </code></pre>
  
  <p>and the error message say:</p>
  
  <pre><code>Traceback (most recent call last):
  
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/basecommand.py", line 122, in main
      status = self.run(options, args)
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/commands/install.py", line 278, in run
      requirement_set.prepare_files(finder, force_root_egg_info=self.bundle, bundle=self.bundle)
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/req.py", line 1177, in prepare_files
      url = finder.find_requirement(req_to_install, upgrade=self.upgrade)
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/index.py", line 194, in find_requirement
      page = self._get_page(main_index_url, req)
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/index.py", line 568, in _get_page
      session=self.session,
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/index.py", line 670, in get_page
      resp = session.get(url, headers={"Accept": "text/html"})
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/_vendor/requests/sessions.py", line 395, in get
      return self.request('GET', url, **kwargs)
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/download.py", line 237, in request
      return super(PipSession, self).request(method, url, *args, **kwargs)
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/_vendor/requests/sessions.py", line 383, in request
      resp = self.send(prep, **send_kwargs)
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/_vendor/requests/sessions.py", line 486, in send
      r = adapter.send(request, **kwargs)
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/_vendor/requests/adapters.py", line 305, in send
      conn = self.get_connection(request.url, proxies)
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/_vendor/requests/adapters.py", line 206, in get_connection
      except_on_missing_scheme(proxy)
  File "/usr/local/python3.5/lib/python3.5/site-packages/pip-1.5.5-py3.5.egg/pip/_vendor/requests/utils.py", line 631, in except_on_missing_scheme
      raise MissingSchema('Proxy URLs must have explicit schemes.')
  pip._vendor.requests.exceptions.MissingSchema: Proxy URLs must have explicit schemes.
  </code></pre>
  
  <p>By the way, I remember if the username or password has the interpunction like "." it must be replaced with something but I forget about that. Can anyone remind me of that? Thanks!</p>