[STORM-3855] Remove python2 support and move to python3. (#3475)

* [STORM-3855] Remove python2 support and move to python3.

* [STORM-3855] Change argument and I/O processing.

* [STORM-3855] Add test_storm.py

* [STORM-3855] PEP8 format,  global var initialization, fix shell_command return value, simpify regex, use log.warning

* [STORM-3855] Add test class for docker-to-squash.py (which must be later renamed to docker_to_squash.py)

* [STORM-3855] Convert byte array to string; initialize variable

* [STORM-3855] Convert bytes to str immediatelly after reading from URL and eliminate unnecesary string conversions.

* [STORM-3855] Reduce indent for main() call.

* [STORM-3855] Remove unused imports

* [STORM-3855] Add latest docker-to-squash from https://git.ouryahoo.com/hadoop/Hadoop/blob/y-branch-2.10/hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/bin/docker-to-squash.py

* [STORM-3855] Change to python3; add license; PEP8 format; rename returncode to rc; log.warn to log.warning; fix working_dir assignment;

* [YSTORM-3855] Remove __init__.py in bin directory.
21 files changed