Allow running Python tests on one section of the codebase

IPython/testing/iptestcontroller.py

@@ -224,7 +224,8 b' def prepare_controllers(options):'
     testgroups = options.testgroups
 
     if testgroups:
-        py_testgroups = [g for g in testgroups if g in py_test_group_names]
+        py_testgroups = [g for g in testgroups if (g in py_test_group_names) \
+                                                or g.startswith('IPython')]
         js_testgroups = [g for g in testgroups if g in js_test_group_names]
     else:
         py_testgroups = py_test_group_names