continued refactoring of filters for django 1.11 compatibility
continued refactoring of filters for django 1.11 compatibility

yan99uic/django-DefectDojo,grendel513/django-DefectDojo,OWASP/django-DefectDojo,OWASP/django-DefectDojo,rackerlabs/django-DefectDojo,rackerlabs/django-DefectDojo,yan99uic/django-DefectDojo,OWASP/django-DefectDojo,grendel513/django-DefectDojo,OWASP/django-DefectDojo,rackerlabs/django-DefectDojo,yan99uic/django-DefectDojo,grendel513/django-DefectDojo,OWASP/django-DefectDojo,grendel513/django-DefectDojo,yan99uic/django-DefectDojo,rackerlabs/django-DefectDojo