@staticmethod<EOL><INDENT>def declare_file(name, <EOL>rc_name=None, environ_name=None, filter=None,<EOL>default_value=None, fail_value=None):<DEDENT>
def _check_file(path):<EOL><INDENT>if not os.path.isfile(path):<EOL><INDENT>raise ValueError('<STR_LIT>' % path)<EOL><DEDENT>return path if filter is None else filter(path)<EOL><DEDENT>return config.declare_path(name, rc_name=rc_name, environ_name=environ_name,<EOL>filter=_check_file, default_value=default_value,<EOL>fail_value=fail_value)<EOL>
config.declare_file(...) is equivalent to config.declare_path(...) except that it
  additionally requires that the path be a file (i.e., not a directory).