Code review comment for lp:~dimitern/maas/bug-994887-nodes-listing-does-not-support-sorting

I've run the tests in test_views_nodes.py and the test coverage report says that 25% of the module sortable.py is untested. This means that some tests are missing or that some of the code in sortable.py is unnecessary and thus you should consider removing it.

$ ./bin/maas test src/maasserver/tests/test_views_nodes.py --with-coverage --cover-package=maasserver.templatetags
[...]
........................................................................S...
Name Stmts Miss Cover Missing
------------------------------------------------------------------
maasserver.templatetags 0 0 100%
maasserver.templatetags.field_type 8 0 100%
maasserver.templatetags.sortable 83 21 75% 47, 51-55, 65-66, 68-69, 124-125, 133-134, 141-142, 151-152, 156-157, 161-162
------------------------------------------------------------------
TOTAL 91 21 77%
----------------------------------------------------------------------
Ran 76 tests in 23.961s