I think it makes sense that itertools should pass on throw, etc. I'd be interested in whether anything would break on this change.
I don't think I like the other suggestions. Having an exception in some random part of a loop throw *into* the iterator of the loop, just seems weird. For the examples, you give, couldn't break_ do the throw itself?
for line in filex:
if test1(line): break
for line in filex: ...
This example convinces me that 3 could introduce untold chaos into existing code. Wouldn't something like this make more sense?
for line in filex: if test1(line): break finally: filex.close()
(And yes, I know the time machine can do that with one extra word and perhaps with handles this better.)
To get __enter__ and __exit__ behavior for an iterator, can't you just wrap it in class that provides that capability and calls close? You might need itertools to have some support that extended iterator class but that seems simpler.