Deprecation warnings

[Eric Harper]

Need to be able to suppress if user wants easily

[Carl Simon Adorf]

Aren't they ignored by default?

[Carl Simon Adorf]

The DeprecationWarning and PendingDeprecationWarning are ignored by default. You need to run python for example with the -W once to display them.

[Eric Harper]

I think I set the ones in v0.4rc to be higher priority so that people don't ignore it, but that also means that it's a bit annoying.

[Carl Simon Adorf]

Instead of changing the reasonable default behavior I strongly recommend to advertise the usage of "-W once".

People will learn immediately to follow that advise when their scripts fail after ignoring this.

[Eric Harper]

Yeah, I think this is the best way.