docs: def setup(self, proxystr='', prompting=True):
          """
          Sets the proxy handler given the option passed on the command
          line.  If an empty string is passed it looks at the HTTP_PROXY
          environment variable.
          """
          self.prompting = prompting
          proxy = self.get_proxy(proxystr)
          if proxy:
              proxy_support = urllib2.ProxyHandler({"http": proxy, "ftp": proxy})
              opener = urllib2.build_opener(proxy_support, urllib2.CacheFTPHandler)
              urllib2.install_opener(opener)