gh-130821: Add type information to wrong type error messages

[donbarbos]

I got next output for use case from issue:

Foo.__int__() must return an int, not NoneType Foo.__float__() must return a float, not NoneType Foo.__bytes__() must return a bytes, not NoneType Foo.__complex__() must return a complex, not NoneType Foo.__bool__() must return a bool, not NoneType Foo.__str__() must return a str, not NoneType 

but we still have a lot of other places where wrong type errors have inconsistent messages. should they be updated too?

• Issue: Inconsistent error messages when returning the wrong type for the type-conversion magic methods #130821

[jstasiak]

Drive-by comment: does it make sense to have tests for these changes?

[donbarbos]

Drive-by comment: does it make sense to have tests for these changes?

it seems that we don't check the text of error messages if we don't want to check the error type itself

[JelleZijlstra]

I think many of the changes in wording are not clear improvements.

[JelleZijlstra]

I don't see much reason to change this error message either.

[donbarbos]

I changed it to the more common way as you recommended elsewhere: __method__() must return an int, not ...
and added type info before method name, like for other methods

[JelleZijlstra]

Here I strongly prefer the old message. Iterable is not a type, it's a category of types.

[donbarbos]

what do you think about new message: "%T.%U() must return an iterable, not %T"

[skirpichev]

I don't think new message adds something bad. Why someone might think, that iterable is a type here? (Another similar case, where new messages mention an iterator.)

[donbarbos]

Why someone might think, that iterable is a type here?

it's just that in the previous iteration the error message was the phrase "must return type ..." :)

[serhiy-storchaka]

LGTM. 👍

[donbarbos]

Thank you everyone for review