Hi Carol, 

> Matthias, Did you wish to mark this issue for additional Documentation and as a behavior change request (warning of signature change until 3.6) in addition to Devguide?

Hum, probably, I'm not super familiar with this bug tracker and it use, I've tried to select both Devguide and Docs now.

> a) Should `ast` shim the old signature and raise a warning until 3.6?

From Guido's comment on linked issue, I guess not: 

> "There is no compatibility guarantee for the ast module"


> b) What additional items should be added to Documentation or Porting Guide?

I guess that Call api changed in the what's new. A link to a rough implementation that show how to get code compatible on 3.5 and below would be nice, it is kind of painful to iterate through the new AST structure and figure things out.

> c) What items should be added to Devguide?

I can talk to Thomas Kluyver tomorrow about merging green tree snake into the devguide, or maybe into ast docs. Would that be useful/more acceptable than linking to external docs ?

Thanks.