Hi Serhiy,

I have done some more investigation this morning and I have come across two distinct issues.

The first is that pickles (specifically the pickle in my earlier message) created in python 3.0->3.4.3 do not load on python 2.7.10. The exception is 3.5.1, which produces a pickle that DOES load on 2.7.10
This is unfortunate but not a regression

The second issue is that pickles created by python 3.0->3.4.3 do NOT load in python 3.5

This is a regression, in the sense that the pickle created by 3.0->3.4.3 is compatible with every other version of python (I haven't tested every single combination here, but several)

From the language perspective, it may be that 3.4.X has incorrect code, but from a compatibility perspective, 3.5 is breaking the promise that pickles are compatible across versions of python.

I write this as justification that python 3.5 should fix this regression in compatibility with 3.0 -> 3.4.3. At the very least 3.5 should have a shim behavior to fallback and allow it to import these pickles correctly.

Thanks,
Anil