Upgrade linting and remove py2 support
-r pip.txt
-# We need these special cases of Python < 3 because we run tests with
-# Python 2 still
# prospector 1.1.6.2 is not compatible with 2.1.0
-astroid==2.0.4; python_version > '3'
-astroid<1.7; python_version < '3'
+astroid<2.1.0
# prospector 1.1.6.2 is not compatible with 2.2.2
-pylint==2.1.1; python_version > '3'
-pylint<2; python_version < '3'
-# prospector 1.1.6.2 is not compatible with 2.0.5
-pylint-django==2.0.2; python_version > '3'
-pylint-django<0.12; python_version < '3'
+pylint<2.2.2
+pylint-django<2.0.5
pylint-celery==0.3
prospector==1.1.6.2
# prospector 1.1.6.2 is not compatible with 2.0.0
