'Same as HTTP(S)ConnectionPool.urlopen, ``url`` must be absolute.'

def urlopen(self, method, url, redirect=True, **kw):

    u = parse_url(url)
    if (u.scheme == 'http'):
        kw['headers'] = self._set_proxy_headers(url, kw.get('headers', self.headers))
    return super(ProxyManager, self).urlopen(method, url, redirect, **kw)
