Add general error message to NodesAssignmentForm
Add general error message to NodesAssignmentForm

Task: 19612
Story: 2001990
Change-Id: I5c6de6726c202c2a631d78a2c7890db5fd2d5b7b

knowncitizen/tripleo-ui,knowncitizen/tripleo-ui,knowncitizen/tripleo-ui,knowncitizen/tripleo-ui