2.12.2: update black, cleanup static check rules

(cherry picked from commit 07682d127e53c144af49734c80ff4d4551800807)

fix ExecResult str & pep8 false-negative

(cherry picked from commit e59514f9ceec8d5172220d2e23d9c446178205bd)

Update MyPy

Now logging is correctly inspected and should not be scipped in
typecheck.

(cherry picked from commit 6fc5cfc6816992ed65897fd6597fee97cd8dc8ab)

Update static checks and make code better

* doc8 -> better docs
* pylint reconfigure and switch logging to python 3.6 f-strings
* drop not used logger instances
* use better global const naming
* drop py2 related config from pylint (master is py3.6+ only)
* better .editorconfig - default indent style is 2, 4 is for python only

(cherry picked from commit b7cee77e76f7d70a5f13a58c8d3f3833bfbd02ec)

Switch travis, optimize editorconfig

(cherry picked from commit 14ce05f9651d16d5a753d195d9217fd18cf2cfe4)

Better pylint and more docstrings in code

(cherry picked from commit ebc36e9a8f22c6444d4eea578f86602d082c4ded)
Signed-off-by: Aleksei Stepanov <penguinolog@gmail.com>