All of the removed `from __future__ import` were needed in older
versions of Python (mostly 2.5.x and below) but later became mandatory
in most versions of Python 3 hence are not necessary anymore.
More specifically, according to __future__.py[1]:
- unicode_literals is part of Python since versions 2.6.0 and 3.0.0;
- print_function is part of Python since versions 2.6.0 and 3.0.0;
- absolute_import is part of Python since versions 2.5.0 and 3.0.0;
- division is part of Python since versions 2.2.0 and 3.0.0;
Get rid of those unnecessary imports to slightly clean up the codebase.
[1] https://github.com/python/cpython/blob/master/Lib/__future__.py
