def _parsearg(self, arg):
parts = str(arg).split("<STR_LIT>")<EOL>if self.config.option.pyargs:<EOL><INDENT>parts[<NUM_LIT:0>] = self._tryconvertpyarg(parts[<NUM_LIT:0>])<EOL><DEDENT>relpath = parts[<NUM_LIT:0>].replace("<STR_LIT:/>", os.sep)<EOL>path = self.config.invocation_dir.join(relpath, abs=True)<EOL>if not path.check():<EOL><INDENT>if self.config.option.pyargs:<EOL><INDENT>raise UsageError(<EOL>"<STR_LIT>" + arg + "<STR_LIT>"<EOL>)<EOL><DEDENT>raise UsageError("<STR_LIT>" + arg)<EOL><DEDENT>parts[<NUM_LIT:0>] = path.realpath()<EOL>return parts<EOL>
return (fspath, names) tuple after checking the file exists.