'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.'

def setup(self, proxystr='', prompting=True):

    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)
