checkWhitespaces :: String -> Maybe CheckError
checkWhitespaces str | whitespaceOk str = Nothing
                     | otherwise = Just TrailingWhitespaces
checkWhitespaces :: String -> Maybe CheckError
checkWhitespaces str | whitespaceOk str = Nothing
                     | otherwise = Just TrailingWhitespaces
checkWhitespaces str | whitespaceOk str = Nothing
                     | otherwise = Just TrailingWhitespaces