fix issue322: tearDownClass is not run if setUpClass failed. Thanks

Mathieu Agopian for fixing.  The patch moves handling setUpClass
into a new autofixture. (XXX impl-decide if rather adding addfinalizer()
API to node's would have a similar effect)

CHANGELOG

@@ -1,6 +1,11 @@
 Changes between 2.3.5 and 2.4.DEV
 -----------------------------------
 
+- fix issue322: tearDownClass is not run if setUpClass failed. Thanks
+  Mathieu Agopian for fixing.  The patch moves handling setUpClass
+  into a new autofixture. (XXX impl-decide if rather adding addfinalizer()
+  API to node's would have a similar effect)
+
 - fix issue336: autouse fixture in plugins should work again.
 
 - change to use hyphen-separated long options but keep the old spelling

_pytest/unittest.py

@@ -28,6 +28,7 @@ def _xunit_setUpClass(request):
         return  # skipped
     setup = getattr(request.cls, 'setUpClass', None)
     teardown = getattr(request.cls, 'tearDownClass', None)
+    if setup is not None:
         setup()
     if teardown is not None:
         request.addfinalizer(teardown)