def _read_configuration_file(self, config_filename):
config = configparser.ConfigParser()<EOL>config.read(config_filename)<EOL>self._source_directory = config.get('<STR_LIT>', '<STR_LIT>')<EOL>self._source_file_extension = config.get('<STR_LIT>', '<STR_LIT>')<EOL>self._source_file_encoding = config.get('<STR_LIT>', '<STR_LIT>')<EOL>self.__shadow_directory = config.get('<STR_LIT>', '<STR_LIT>', fallback=None)<EOL>self._pystratum_metadata_filename = config.get('<STR_LIT>', '<STR_LIT>')<EOL>self._constants_class_name = config.get('<STR_LIT>', '<STR_LIT:class>')<EOL>
Reads parameters from the configuration file.

:param str config_filename: The name of the configuration file.