Make sure we properly close the bzr WorkingTree in our Authors up-to-datedness unit test.

nova/tests/misc_unittest.py

@@ -30,6 +30,7 @@ class ProjectTestCase(test.TrialTestCase):
             import bzrlib.workingtree
             tree = bzrlib.workingtree.WorkingTree.open('..')
             tree.lock_read()
+            try:
                 parents = tree.get_parent_ids()
                 g = tree.branch.repository.get_graph()
                 for p in parents[1:]:
@@ -50,3 +51,5 @@ class ProjectTestCase(test.TrialTestCase):
 
                 self.assertTrue(len(missing) == 0,
                                 '%r not listed in Authors' % missing)
+            finally:
+                tree.unlock()