test-clone: discard lock-related messages We can't predict where those will show up and they're not super-important for the contents of this particular test, so just drop them. Further reduces the flakiness of the test to zero.

test-clone: fix some instability in pooled clone race condition test Healthy output (one log file mentioning "existing pooled" and one mentioning "new pooled") will now print in a stable order, but unhealthy output will print some sort of error. This reduces the flakiness of the test from 55% to 38%. My next patch makes it completely stable.

py3: add an os.fsencode backport to ease path handling

py3: a second argument to open can't be bytes This fixes open(filename, 'r'), open(filename, 'w'), etc. calls. In Python 3, that second argument *must* be a string, you can't use bytes. The fix is the same as used with getattr() (where the second argument must also always be a string); in the tokenizer, where we detect calls, if there is something that looks like a call to open (and is not an attribute, so the previous token is not a "." dot) then make sure that that second argument is not converted to a `bytes` object instead. There is some remaining issue where the current transformer will also rewrite open(f('foo')). However this also affect function for which we perform similar rewrite ('getattr', 'setattr', 'hasattr', 'safehasattr') and will be dealt with in a follow up.

py3: make check-py3-compat.py import importlib only if necessary importlib isn't available on Python 2.6, and it isn't necessary for Py2 checks.

templater: handle division by zero in arithmetic For now, just turn it to an abort.