Easy debugging.

Show sorted list, as sorting does not impact sets equality, and, if possible,
format a list in human readable way.

product/ERP5Type/tests/ERP5TypeTestCase.py

@@ -603,7 +603,12 @@ class ERP5TypeTestCaseMixin(ProcessingNodeTestCase, PortalTestCase):
 
     def failIfDifferentSet(self, a, b, msg=""):
       if not msg:
-        msg='%r != %r' % (a, b)
+        try:
+          from pprint import pformat
+        except ImportError:
+          msg='%r != %r' % (sorted(a), sorted(b))
+        else:
+          msg='\n%s\n!=\n%s' % (pformat(sorted(a)), pformat(sorted(b)))
       self.assertEquals(set(a), set(b), msg)
     assertSameSet = failIfDifferentSet