Perform minor code cleanup.
Perform minor code cleanup.

* Make code more PEP8-compliant through adding missing spaces after semicolons.
  E.g. "def foo(a,b): ..." -> "foo(a, b): ...".
* Complete Python 2 <-> Python 3 compatibility transition by adding
  missing parenthesis in several "print" function calls.

yandexdataschool/Practical_RL,yandexdataschool/Practical_RL