--- xulrunner-27.0/mozilla/python/mozbuild/mozbuild/virtualenv.py~	2013-05-11 21:19:23.000000000 +0200
+++ xulrunner-27.0/mozilla/python/mozbuild/mozbuild/virtualenv.py	2013-05-14 22:51:32.136719267 +0200
@@ -300,9 +300,7 @@
 
         args = [
             self._base_python,
-            os.path.join(
-                self.topsrcdir, "third_party", "python", "virtualenv", "virtualenv.py"
-            ),
+            '/usr/bin/virtualenv-3',
             # Without this, virtualenv.py may attempt to contact the outside
             # world and search for or download a newer version of pip,
             # setuptools, or wheel. This is bad for security, reproducibility,