getting bound methods requires handler name

[rmorshea]

Retrieving bound methods from event handlers is only valid if their name attribute is not None (i.e. they were registered with @observe). Without checking that name is not None, EventHandler instances registered using HasTraits.observe will fail.

[minrk]

@rmorshea is there a test we can add?

[SylvainCorlay]

@rmorshea in which case would we use an EventHandler that is not used as a descriptor?

[rmorshea]

@SylvainCorlay, I think you're right - adding a test as if registering unbound event handlers is a feature doesn't seem right. However the error that arises, if you were to use unbound event handlers, isn't indicative of what went wrong, so checking that name is not None still seems like a good idea.

[minrk]

Do we want to merge this (with a confirming test) before 4.1? I think I've done the testing I need for the downstream verifications that we are actually backwards-compatible, so we should be able to release this week. I'm just not sure which side of the release this sits on.

[SylvainCorlay]

I am fine with this, but I don't think that this should be required.