Fix validation of dynamic Enum inside a Tuple

[mdickinson]

This PR fixes validation of dynamic enumerations inside a Tuple. Previously, for the dynamic case of an Enum, no validation was performed until trait-set time. This PR changes the logic so that the validate method (which the Tuple uses for its item validation) is no longer None.

This fixes the issue originally reported in #1385. There are other issues identified in the #1385 comments that still need to be fixed (or have new issues opened) before #1385 can be closed.

Checklist

• Tests
• Update API reference (docs/source/traits_api_reference) N/A
• Update User manual (docs/source/traits_user_manual) N/A
• Update type annotation hints in traits-stubs N/A

[mdickinson]

Unrelated drive-by fix in this line, fixing copypasta ("range" -> "enum")

[kitchoi]

LGTM

[mdickinson]

Thanks @kitchoi for reviewing. I added the new test (for a dynamic Enum inside a List) back in; it was failing before because I messed up the trait names. (Possibly a reason to use HasStrictTraits instead of HasTraits even when writing tests.)

[kitchoi]

Thank you! Still LGTM. So this PR can close #1385 then?

[mdickinson]

So this PR can close #1385 then?

Yes, I guess so. I've opened an issue for the Tuple exception-silencing (#1389). I need to open an issue, or create a fix, for the corresponding issue in BaseRange.