django-filter upgrade with message

Author: humitos

requirements/pip.txt

@@ -27,7 +27,13 @@ django-extensions==2.1.3
 djangorestframework==3.9.0
 
 # Filtering for the REST API
-django-filter==2.0.0
+# When Python2 gets deprecated we can upgrade django-filter
+# >   from .filterset import FilterSet
+# E     File "/home/travis/build/rtfd/readthedocs.org/.tox/py27/lib/python2.7/site-packages/django_filters/filterset.py", line 184
+# E       def __init__(self, data=None, queryset=None, *, request=None, prefix=None):
+# E                                                     ^
+# E   SyntaxError: invalid syntax
+django-filter<2.0.0
 
 django-vanilla-views==1.0.5
 jsonfield==2.0.2