Added a test case for the saxutils.prepare_input_source setSystemId bug.
diff --git a/Lib/test/test_sax.py b/Lib/test/test_sax.py
index 59e14c5..b4c840b 100644
--- a/Lib/test/test_sax.py
+++ b/Lib/test/test_sax.py
@@ -185,6 +185,18 @@
 #
 # ===========================================================================
 
+# ===== XMLReader support
+
+def test_expat_file():
+    parser = create_parser()
+    result = StringIO()
+    xmlgen = XMLGenerator(result)
+
+    parser.setContentHandler(xmlgen)
+    parser.parse(open(findfile("test.xml")))
+
+    return result.getvalue() == xml_test_out
+
 # ===== DTDHandler support
 
 class TestDTDHandler: