Fix unicode test for Python 3.

IPython/core/tests/test_interactiveshell.py

@@ -226,5 +226,5 b' class TestSystemRaw(unittest.TestCase):'
     def test_1(self):
         """Test system_raw with non-ascii cmd
         """
-        cmd = ur'''python -c "u'åäö'"   '''
+        cmd = ur'''python -c "'åäö'"   '''
         _ip.shell.system_raw(cmd)