Several tests in test_snapwell_norne are failing

[oyvindeide]

Some tests are marked as xfail in test_snapwell_norne.py, we need to figure out why.

Relevant tests:

• snapwell/tests/test_snapwell_norne.py

  Line 22 in f07c25b

  def test_snapwell_invalid_arg_throws(self):

• snapwell/tests/test_snapwell_norne.py

  Line 28 in f07c25b

  def test_snapwell_well_ok(self):