sort by class name since types are not orderable in py3

src/zope/testrunner/runner.py

@@ -884,9 +884,13 @@ def layer_from_name(layer_name):
 def order_by_bases(layers):
     """Order the layers from least to most specific (bottom to top)
     """
-    layers = [layer for layer in layers]
     getmro = inspect.getmro
-    layers.sort(key=lambda x: getmro(x)[::-1])
+
+    def layer_sortkey(layer):
+        return (c.__name__ for c in getmro(layer)[::-1])
+
+    layers = [layer for layer in layers]
+    layers.sort(key=layer_sortkey)
     gathered = []
     for layer in layers:
         gather_layers(layer, gathered)