Turn deprecation warnings into error ?

[Carreau]

What do you think ?

Should we try and see how many we have?

[takluyver]

Doesn't Python already have an option to turn warnings into errors? It doesn't seem high priority to me, though.

[Carreau]

A global one, you cannot filter by category. (-We IIRC.) we likely don't want deprecation warning from all over the place to actually fail, you want to error only on a few, default other, and completely ignore some other. I was mostly thinking of show all those that come from IPython itself, and once we update the API turn them into error to be sure not to reintroduce old API. Typically traitlets 4.2 @observe...