Warnings: coroutine 'ClientSession.close' was never awaited

[nicoddemus]

I've seen this warnings in bottery's CI:

c:\projects\bottery\.tox\py35\lib\site-packages\bottery\bottery.py:107: RuntimeWarning: coroutine 'ClientSession.close' was never awaited
  self.session.close()
c:\projects\bottery\.tox\py35\lib\site-packages\bottery\bottery.py:107: RuntimeWarning: coroutine 'ClientSession.close' was never awaited
  self.session.close()

Seems like that line should be await self.session.close(), correct?