update changelog; add skipif in parallel tests to check for graphviz

Changelog.md

@@ -3,6 +3,7 @@
 ## 0.8.5 ()
 
 - `AsyncMachine.switch_model_context` is expected to be `async` now for easier integration of async code during model switch.
+- Bugfix #478: Initializing a machine with `GraphSupport` threw an exception when initial was set to a nested or parallel state (thanks @nickvazztau)
 
 ## 0.8.4 (October 2020)
 

tests/test_parallel.py

@@ -8,6 +8,9 @@
 from transitions.extensions.nesting import NestedState as State, _build_state_list
 from transitions.extensions import HierarchicalGraphMachine
 from .test_nesting import TestNestedTransitions as TestNested
+from .test_pygraphviz import pgv
+from .test_graphviz import pgv as gv
+from unittest import skipIf
 
 try:
     from unittest.mock import MagicMock
@@ -193,6 +196,7 @@ def test_model_state_conversion(self):
         self.assertEqual(states, _build_state_list(tree, sep))
 
 
+@skipIf(pgv is None, "pygraphviz is not available")
 class TestParallelWithPyGraphviz(TestParallel):
 
     def setUp(self):
@@ -206,6 +210,7 @@ def __init__(self, *args, **kwargs):
         self.machine_cls = PGVMachine
 
 
+@skipIf(gv is None, "graphviz is not available")
 class TestParallelWithGraphviz(TestParallel):
 
     def setUp(self):