Return a signature for use in GET requests

def _get_file(self, prefixed_name):
        """
        Return a signature for use in GET requests
        """
        headers = self._request_headers('GET', prefixed_name)
        file = S3ContentFile('')
        with closing(HTTPConnection(self.netloc)) as conn:
            conn.request('GET', prefixed_name, headers=headers)
            response = conn.getresponse()
            if not response.status in (200,):
                if response.length is None:
                    # length == None seems to be returned from GET requests
                    # to non-existing files
                    raise S3FileDoesNotExistError(prefixed_name)
                # catch all other cases
                raise S3IOError(
                    'py3s3 GET error. '
                    'Response status: {}. '
                    'Reason: {}. '
                    'Response Text: \n'
                    '{}'.format(response.status, response.reason, response.read()))

            file = S3ContentFile(response.read())
        return file