Python 2 deprecation

January 1st of 2020 is the EOL for Python2. I would say it makes sense to start working on python client version 2 (for us this is going to be 1.0.0), which only supports python 3 (preferably Python 3.7+)

List of things I would like to see in the new major release (suggestion are highly welcome):

• Explicit types declarations (use typing module) -> High priority
• asyncio and async/await usage (for both network and file system i/o operations) -> Medium to Low priority, this might be a serious change and might require the users to update a lot of their code
• Proper exceptions inheritance (use raise from) -> High priority
• Ordered dictionaries usage -> High priority
• Proper strings/bytearrays usage -> High priority
• Proper super usage -> High priority
• pytest usage -> Medium priority

[mykola-mokhnach]

One more useful thing which is present since Python 3.7 and which we could use:

• Data classes

[ki4070ma]

Done