Stream the MediaFile to the filesystem.

def fetch_to_file(self, filename):
        """Stream the MediaFile to the filesystem."""
        self.filename = filename
        stream = self.client.get_iter_content(self.uri)
        content_type = self.client.response_headers['content-type']

        if content_type in _content_type_map:
            self.fileext = _content_type_map[content_type]
            self.filename = "%s.%s" % (self.filename, self.fileext)

        with open(self.filename, 'wb') as file_handle:
            for chunk in stream:
                file_handle.write(chunk)