* async is a keyword in python3.7
Setting up patroni (1.4.4-1) ...
File "/usr/lib/python3/dist-packages/patroni/ha.py", line 610
'offline': dict(stop='fast', checkpoint=False, release=False, offline=True, async=False),
^
SyntaxError: invalid syntax
Fix#750 by replacing dict member "async" with "async_req".
* requirements.txt: Update for new kubernetes version compatible with 3.7