py3: remove hack that removed flush argument from print() calls on Python 2

py3: remove long() compatibility code

zeroconf: constant-fold a `pycompat.ispy3` I’ve checked that both bytes and str gets passed as the `name` parameter, so the rest of the condition is still required. Because there aren’t really any tests for the extensions, I didn’t want to refactor it to pass a single type.

py3: remove conditional to import collections.abc.MutableMapping