Fix tests error after django-condtance integration

.travis.yml

opds_catalog/dl.py

opds_catalog/feeds.py

opds_catalog/inpx_parser.py

opds_catalog/management/commands/sopds_scanner.py

opds_catalog/management/commands/sopds_server.py

opds_catalog/opds_middleware.py

opds_catalog/settings.py

opds_catalog/sopdscan.py

opds_catalog/tests/test_feeds.py

opds_catalog/tests/test_models.py

opds_catalog/tests/test_scan.py

sopds_web_backend/views.py