Fix testRequiredHeaderDisappears()

Author: Simon Warta

integrationtests.py

@@ -324,7 +324,12 @@ def testRequiredHeaderDisappears(self):
             subprocess.check_call(compileCmd)
 
             os.remove("info.h")
-            subprocess.check_call(compileCmd)
+
+            # real compiler fails
+            process = subprocess.Popen(compileCmd, stdout=subprocess.PIPE)
+            stdout, _ = process.communicate()
+            self.assertEqual(process.returncode, 2)
+            self.assertTrue("C1083" in stdout.decode(clcache.CL_DEFAULT_CODEC))
 
     # When a header included by another header becomes obsolete and disappers,
     # we must fall back to real compiler.