Description:
The package python-pylint depends on python-astroid with version constraints <2.0,>=1.6.
These are missing from the package resulting in a broken / unsuable python-pylint installation after the upgrade to python-astroid 2.0-1.

Additional info:
* pytlin-1.9.2-1


Steps to reproduce:
* Upgrade your system.
* Install pylint.
* Run pylint
* Get:
Traceback (most recent call last):
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 570, in _build_master
ws.require(__requires__)
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 888, in require
needed = self.resolve(parse_requirements(requirements))
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 779, in resolve
raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.ContextualVersionConflict: (astroid 2.0 (/usr/lib/python3.6/site-packages), Requirement.parse('astroid<2.0,>=1.6'), {'pylint'})

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/usr/bin/pylint", line 6, in <module>
from pkg_resources import load_entry_point
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3095, in <module>
@_call_aside
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3079, in _call_aside
f(*args, **kwargs)
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3108, in _initialize_master_working_set
working_set = WorkingSet._build_master()
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 572, in _build_master
return cls._build_from_requirements(__requires__)
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 585, in _build_from_requirements
dists = ws.resolve(reqs, Environment())
File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 774, in resolve
raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'astroid<2.0,>=1.6' distribution was not found and is required by pylint