Test error messages

[Smit-create]

#408 (review)

[certik]

In the future, we can improve these messages, here is an idea:

Suggested change

	6 | a.append(4, 5)
	| ^^^^^^^^^^^^^^
	6 | a.append(4, 5)
	| ^^^^^^ ┬ ┬
	| │ └──┴── two arguments provided
	| │
	| expected one argument

This is how it looks like in a terminal (without colors):

And of course there would be colors.

I posted this comment at #398 (comment) so that we don't forget.

[certik]

This looks perfect, thank you!