'division_safe' fix applied

[vilnius-dev]

This fix used instead of libfuturize.fixes.fix_division.

Division
Integer division (rounding down):

# Python 2 only:
assert 2 / 3 == 0

# Python 2 and 3:
assert 2 // 3 == 0

“True division” (float division):

# Python 3 only:
assert 3 / 2 == 1.5

# Python 2 and 3:
from __future__ import division    # (at top of module)

assert 3 / 2 == 1.5

“Old division” (i.e. compatible with Py2 behaviour):

# Python 2 only:
a = b / c            # with any types

# Python 2 and 3:
from past.utils import old_div

a = old_div(b, c)    # always same as / on Py2

[cmsdmwmbot]

Jenkins results:

• Unit tests: succeeded
  • 2 changes in unstable tests
• Pylint check: failed
  • 362 warnings and errors that must be fixed
  • 56 warnings
  • 1611 comments to review
• Pycodestyle check: succeeded
  • 2947 comments to review
• Python3 compatibility checks: succeeded
  • there are suggested fixes for newer python3 idioms

Details at https://cmssdt.cern.ch/jenkins/view/All/job/DMWM-WMCore-PR-test/5665/artifact/artifacts/PullRequestReport.html

[ericvaandering]

This one, I think, requires some thought and we should make an attempt to discern which of these things are expecting ints and which are expecting floats as a result.

This will take some effort, but will leave us with better, less ugly code.

[vilnius-dev]

@ticoann As we discussed on meeting this PR could be closed.
I making changes "by hand", results can be viewed here: #8125