def processed_file(self, new_text, filename, old_text=None, write=False,
                       encoding=None):
        """
        Called when a file has been refactored and there may be changes.
        """
        self.files.append(filename)
        if old_text is None:
            old_text = self._read_python_source(filename)[0]
            if old_text is None:
                return
        equal = old_text == new_text
        self.print_output(old_text, new_text, filename, equal)
        if equal:
            self.log_debug("No changes to %s", filename)
            if not self.write_unchanged_files:
                return
        if write:
            self.write_file(new_text, filename, old_text, encoding)
        else:
            self.log_debug("Not writing changes to %s", filename)
Called when a file has been refactored and there may be changes.