Strip long suffix from integers.

### Motivation
One more small step towards porting the codebase to Python 3.

### Changelog
* Strip `L` suffix from integer quantities. Per [PEP 237](https://www.python.org/dev/peps/pep-0237/), the interpreter chooses the appropriate integer type automatically based on the value.
* Enable `pylint` to warn on use of long suffix.