Fixes graphviz test

I wonder if this is flakey somehow? Anyway adding this to see if circleci complains
or not.

tests/test_graph.py

@@ -362,8 +362,7 @@ def test_create_graphviz_graph():
                        '\tb -> A',
                        '\tc -> A',
                        '\tA -> C',
-                       '}',
-                       ''])
+                       '}'])
     digraph = graph.create_graphviz_graph(nodes, user_nodes, 'test-graph')
     actual = sorted(str(digraph).split('\n'))
     assert actual == expected