Corner cases for admin_promote and admin_demote

unit/test_all.py

@@ -689,6 +689,19 @@ class TestModelverse(unittest.TestCase):
         admin_promote("HUTN")
         admin_demote("HUTN")
 
+        # Unknown user
+        try:
+            admin_promote("user3")
+            self.fail()
+        except UnknownUser:
+            pass
+
+        try:
+            admin_demote("user4")
+            self.fail()
+        except UnknownUser:
+            pass
+
         # Can also demote ourselves again
         admin_demote("user")