Consider removing future as a dependency

[gGonz]

I use zenpy as dependency on a project, we have many months seeing a weird warning while running our tests due to future raising a DeprecationWarning, by using the now deprecated imp module.

Yeah, I know we can just ignore this specific warning, but that seems "dirty". Please note that future has some issues about this, the oldest one has more than 3 years open without any change...
PythonCharmers/python-future#246

In the same issue above, there is a reference to a pysaml2's pull request where the maintainer tells that he will use six instead of future.
IdentityPython/pysaml2#576

Here's the traceback shown when I run our tests with pytest -W error:

================================================================================================ test session starts ================================================================================================
platform linux -- Python 3.7.6, pytest-5.3.5, py-1.8.1, pluggy-0.13.1
django: settings: project.settings.test (from env)
rootdir: /opt/project/project, inifile: pytest.ini
plugins: xdist-1.31.0, factoryboy-2.0.3, cov-2.8.1, django-3.8.0, forked-1.1.3, mock-2.0.0
collecting 0 items / 1 error                                                                                                                                                                                        
====================================================================================================== ERRORS =======================================================================================================
__________________________________________________________________________________ ERROR collecting apps/contracts/api/v1/tests.py __________________________________________________________________________________
/home/python/.cache/pypoetry/virtualenvs/project-soWN0cI--py3.7/lib/python3.7/site-packages/py/_path/local.py:701: in pyimport
    __import__(modname)
apps/contracts/api/v1/__init__.py:1: in <module>
    from .tasks import *  # NOQA
apps/contracts/api/v1/tasks.py:1: in <module>
    from zenpy import Zenpy
/home/python/.cache/pypoetry/virtualenvs/project-soWN0cI--py3.7/lib/python3.7/site-packages/zenpy/__init__.py:6: in <module>
    from zenpy.lib.api import (
/home/python/.cache/pypoetry/virtualenvs/project-soWN0cI--py3.7/lib/python3.7/site-packages/zenpy/lib/api.py:43: in <module>
    from zenpy.lib.response import *
/home/python/.cache/pypoetry/virtualenvs/project-soWN0cI--py3.7/lib/python3.7/site-packages/zenpy/lib/response.py:4: in <module>
    from zenpy.lib.generator import SearchResultGenerator, ZendeskResultGenerator, ChatResultGenerator, ViewResultGenerator, \
/home/python/.cache/pypoetry/virtualenvs/project-soWN0cI--py3.7/lib/python3.7/site-packages/zenpy/lib/generator.py:8: in <module>
    from future.standard_library import install_aliases
/home/python/.cache/pypoetry/virtualenvs/project-soWN0cI--py3.7/lib/python3.7/site-packages/future/standard_library/__init__.py:65: in <module>
    import imp
/usr/local/lib/python3.7/imp.py:33: in <module>
    DeprecationWarning, stacklevel=2)
E   DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! stopping after 1 failures !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! xdist.dsession.Interrupted: stopping after 1 failures !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
================================================================================================= 1 error in 4.53s ==================================================================================================

Any way to have this fixed? 🙏

[facetoe]

AFAIK future is only used to have consistent behaviour for math.ceil in https://github.com/facetoe/zenpy/blob/master/zenpy/lib/generator.py#L19. Happy to accept a patch that solves that issue without the future module.