ProxyFuture infinite recursion in error case?

[rohanpm]

I've observed the following undesirable behavior... I have a proxy future which failed with an exception (OK):

(Pdb) pp x
<ProxyFuture at 0x7fb4e0772a90 state=finished raised AttributeError>
(Pdb) pp x.result()
*** AttributeError: 'str' object has no attribute 'get'

Trying to iterate over this future triggers infinite recursion (not OK):

(Pdb) pp iter(x)
*** RecursionError: maximum recursion depth exceeded while calling a Python object

Expected behavior: it should have raised the underlying exception.