def init_config(config_file=None):
global config<EOL>if config_file and os.path.exists(config_file):<EOL><INDENT>read = config.read([config_file])<EOL>if not read:<EOL><INDENT>raise ValueError(<EOL>"<STR_LIT>" % config_file)<EOL><DEDENT><DEDENT>
Initialize the configuration from a config file.

The values in config_file will override those already loaded from the default
configuration file (defaults.cfg, in current package).

This method does not setup logging.

@param config_file: The path to a configuration file.
@type config_file: C{str}

@raise ValueError: if the specified config_file could not be read.
@see: L{init_logging}