Takes the given response and tries digest-auth, if needed.

def handle_401(self, response, exc=None):
        """Takes the given response and tries digest-auth, if needed."""
        if response.status_code == 401:
            s_auth = response.headers.get('www-authenticate', '')
            if 'digest' not in s_auth.lower():
                return
            request = response.request
            if not request.headers.get('authorization'):
                self.options = parse_dict_header(s_auth.replace('Digest ', ''))
                authorization = self.encode(request.method, request.url)
                params = request.inp_params.copy()
                headers = params.pop('headers', [])
                headers.append(('authorization', authorization))
                params['headers'] = headers
                response.request_again = request_again(request.method,
                                                       request.url,
                                                       params)