Remove EventSource.from_config

[maxnoe]

Please describe the use case that requires this feature.

EventSource.from_config is not needed anymore (and since quite some time), since EventSource(parent=self) "just works™".

@FrancaCassol was confused about what the purpose is. Since it doesn't serve one anymore, we should remove that method.

[kosack]

I didn't even realize it existed! Yes, should remove

[HealthyPear]

Not sure if this is the right place, but the docs are a bit obscure about this part.

They mention that "An EventSource can also be created through the configuration system" which sounds clear, but than they mention both config and parent.

Is it possible to add more lines about this and what is the difference?

config should be a dictionary loaded with the traitlets API, but what's parent?
I looked at some of the unit tests of event source, but it's not really clear even from the code (at least for me)

[kosack]

It comes from the traitlets.config API: you can either construct a Component by

1. passing in trait arguments explicitly SomeComponent(param1=1, param2="x")
2. passing in a traitlets.config.Config dictionary SomeComponent(config=config)
3. referencing a parent Configurable, that already has or will have a config loaded later SomeComponent(parent=self) where self is a Component or Tool (which both inherit from triaitlets.config.HasConfig)

The constructors are overloaded to support all three methods, but generally you should not mix them. E.g. if you specify config=x you should not specify parent=x.