Modified test_execute_DAG_retries

Using `GufeKeys` to further sort DAGs with
`lexicographical_topological_sort`, the execution order of
`ProtocolUnits` for this particular `Protocol` differed from the
original implementation using `topological_sort`. This new sorting
placed the guaranteed-to-fail `ProtocolUnit` later, allowing `ok`
results to accumulate. This change reflects the new ordering,
resulting in 26 total results instead of 5, now accounting for the 21
`SimulationUnits` that complete before `BrokenSimulationUnit` fails.

gufe/tests/test_protocol.py

@@ -701,11 +701,16 @@ def test_execute_DAG_retries(solvated_ligand, vacuum_ligand, tmpdir):
                         n_retries=3)
 
         assert not r.ok()
-        # we did 3 retries, so 4 total failures
-        assert len(r.protocol_unit_results) == 5
-        assert len(r.protocol_unit_failures) == 4
-        assert len(list(shared.iterdir())) == 5
 
+        number_unit_failures = len(r.protocol_unit_failures)
+        number_unit_results = len(r.protocol_unit_results)
+        number_dirs = len(list(shared.iterdir()))
+
+        # failed first attempt of BrokenSimulationUnit, failed 3 retries
+        assert number_unit_failures == 4
+        # InitializeUnit and 21 SimulationUnits run before guaranteed
+        # final failure
+        assert number_unit_results == number_dirs == 26
 
 def test_execute_DAG_bad_nretries(solvated_ligand, vacuum_ligand, tmpdir):
     protocol = BrokenProtocol(settings=BrokenProtocol.default_settings())