Use a TypeError, rather than a ValueError, when refusing to treat a str as a Vec

[alex]

This is far more consistent with how these exceptions are usually used

[adamreichold]

@alex Before we proceed with an API change here, any opinions on #2632 which might remove this code path entirely?

[alex]

I'm pretty ambivalent.

[alex]

Given that #2632 hasn't reached a consensus, would it be appropriate to merge this in the event this code path lives on?

[davidhewitt]

I think it would make sense to merge this, as it's IMO a reasonable correction over what already exists while we decide whether to merge the bigger change.

[davidhewitt]

@adamreichold please forgive me if you disagree!

[adamreichold]

@adamreichold please forgive me if you disagree!

Please don't worry, a disagreement is not an attack, so I don't think there is anything to forgive here.

And while I personally would like #2632 to land, I very much understand that there is no consensus yet and that change should therefore not block reasonable improvements.