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Dubious MRO from mixing classic and new-style classes 
in multiple inheritance:
> def mrolist(k):
> return ' '.join([c.__name__ for c in k.__mro__])
> 
> def f():
> # No question here.
> class C: pass
> class M1(C, object): pass
> print mrolist(M1) # "M1 C object"
> 
> # And no question here.
> class D(C): pass
> class M2(object, D): pass
> print mrolist(M2) # "M2 object D C"
> 
> # Here I expected
> # "M3 M1 M2 object D C"
> # but got
> # "M3 M1 M2 D C object"
> class M3(M1, M2): pass
> print mrolist(M3)
> 
> f()
"""
If I add
 class M4(M2, M1): pass
 print mrolist(M4)
this prints what you may have expected:
 M4 M2 M1 object D C
My conclusion is that it's an artefact of how 
conservative_merge() resolves the conflict between M1 
and M2: in M1, C preceeds object, while in M2, object 
preceeds C. This order conflict is supposed to be
outlawed, but I didn't feel like testing for it -- the 
function serious_order_disagreements() always returns 
false.
In the light of conflicts, the algorithm in 
conservative() apparently favors the order of the 
first base class encountered.
"""

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user_id=6380
Closing as Won't Fix. In the light of conflicts, the MRO
algorithm can yield surprises, yes. Then don't do that.