def process_non_raw_string_token(self, prefix, string_body, start_row):
        '''
        check for bad escapes in a non-raw string.

        prefix: lowercase string of eg 'ur' string prefix markers.
        string_body: the un-parsed body of the string, not including the quote
        marks.
        start_row: integer line number in the source.
        '''
        if 'u' in prefix:
            if string_body.find('\\0') != -1:
                self.add_message('null-byte-unicode-literal', line=start_row)
check for bad escapes in a non-raw string.

        prefix: lowercase string of eg 'ur' string prefix markers.
        string_body: the un-parsed body of the string, not including the quote
        marks.
        start_row: integer line number in the source.