crowdin: Enforce py3 and align style of strings

* This script doesn't really work properly with py2 anymore
* py2 is deprecated anyway
* The style of the various print statements and strings has been a mixture
  of old and new styles
  * Make use of f-strings (string interpolation) -> faster, easier to read
* Adapt README to contain 17.1 branch and mention the proper requirements

Change-Id: Ia9a3a8975ae4ed39f3e7ee08b4cfdb6fe1d6c50f
2 files changed
tree: 06053e9b5f6a8ad4d8d1ec246fa68a5416bb9764
  1. config/
  2. crowdin_sync.py
  3. README.mkdn