serhiy: so, the funny thing is this: your fix is ultimately a reversion. Though we have to dig way back into the bowels of defusedxml to see this. Specifically, to this commit!

https://github.com/tiran/defusedxml/commit/03d4fc6cf246a209c2cf892b33f5b6cf5af4ecbd

that's the point at which Christian introduced a divergence between Python 2 and Python 3 here, and essentially the same divergence remains between the `elif PY3:` and `else: # Python 2.7` blocks now. The Python 2.7 block in current defusedxml is in fact the same as your block, because `_iterparse` is just the parent `iterparse` function, as discovered by `_get_py3_cls()`.

So before applying your change, I kinda want to understand why Christian introduced this divergence in the first place. The commit message claims it's because Python 3.3 hid some pure python, but I don't quite understand that: https://github.com/python/cpython/blob/3.3/Lib/xml/etree/ElementTree.py looks like iterparse() was still perfectly available and usable for this purpose in 3.3, just as it was in 3.2 and still appears to be in 3.6.