def _errstr(value):
value = str(value) <EOL>if len(value) > MAX_ERROR_STR_LEN:<EOL><INDENT>return value[:MAX_ERROR_STR_LEN] + '<STR_LIT>'<EOL><DEDENT>else:<EOL><INDENT>return value<EOL><DEDENT>
Returns the value str, truncated to MAX_ERROR_STR_LEN characters. If
    it's truncated, the returned value will have '...' on the end.