Stream doesn't closes response object

[Roman Skurikhin]

Long story short

When I use container.attach() it opens a connection as expected, but the underlying aiohttp response object is not closed. It leads to a warnings:

ResourceWarning: Unclosed response <ClientResponse(http://10.1.0.19:2375/v1.39/containers/912a83018d776abf6bc7e6ad0a7abca727a1dc8df40e286681abe779b8b3a473/attach?detachKeys=&logs=1&stdin=0&stdout=1&stderr=1&stream=1) [101 UPGRADED]>

• Expected behaviour: no warning, response object closed
• Actual behaviour: warning thrown about unclosed response object.

Additional details:

In the following code

aiodocker/aiodocker/stream.py

Lines 111 to 116 in bb149e8

 async def close(self) -> None: 
     if self._resp is not None: 
         return 
     if self._closed: 
         return 
     assert self._resp is not None 

Line if self._resp is not None: looks very suspicious, I think that the not there is a bug.