deprecation warnings in Python 3.7

[oconnor663]

There are two that I can see:

/usr/lib/python3.7/site-packages/yaml/constructor.py:126: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.ab
c' is deprecated, and in 3.8 it will stop working
  if not isinstance(key, collections.Hashable):

/usr/lib/python3.7/asyncio/coroutines.py:58: DeprecationWarning: 'with (yield from lock)' is deprecated use 'async with lock' instead
  return self.gen.send(None)

[oconnor663]

https://github.com/buildinspace/peru/pull/194 is open to fix this.