Enable test_traceback (#740)

Author: slozier

Src/IronPythonTest/Cases/IronPythonCasesManifest.ini

@@ -198,8 +198,7 @@ Reason=disabled due to https://github.com/IronLanguages/ironpython2/issues/182
 Ignore=true
 
 [IronPython.test_traceback]
-Ignore=true
-Reason=TODO: Needs lots of work
+IsolationLevel=PROCESS
 
 [IronPython.hosting.editor_svcs.test_errorlistener]
 Ignore=true