Fix irunner tests when $PYTHONSTARTUP is set.

Closes gh-2655

IPython/lib/tests/test_irunner.py

@@ -137,7 +137,7 b' In [12]: exit'
 
     def testPython(self):
         """Test the Python runner."""
-        runner = irunner.PythonRunner(out=self.out)
+        runner = irunner.PythonRunner(out=self.out, args=['-E'])
         source = doctest_refactor_print("""
 print 'hello, this is python'