code: def get_proxy(self, proxystr=''):
          
          if not proxystr:
              proxystr = os.environ.get('HTTP_PROXY', '')
          if proxystr:
              if '@' in proxystr:
                  user_password, server_port = proxystr.split('@', 1)
                  if ':' in user_password:
                      user, password = user_password.split(':', 1)
                  else:
                      user = user_password
                      prompt = 'Password for %s@%s: ' % (user, server_port)
                      password = urllib.quote(getpass.getpass(prompt))
                  return '%s:%s@%s' % (user, password, server_port)
              else:
                  return proxystr
          else:
              return None
docs: Get the proxy given the option passed on the command line.
          If an empty string is passed it looks at the HTTP_PROXY
          environment variable.