Add preparers for python

Bug: 181070625
Test: m nothing
Change-Id: I590ad62db6fd62719c83286780563cf6d55e3e17
diff --git a/python/python.go b/python/python.go
index a078c0b..4444a70 100644
--- a/python/python.go
+++ b/python/python.go
@@ -29,7 +29,11 @@
 )
 
 func init() {
-	android.PreDepsMutators(RegisterPythonPreDepsMutators)
+	registerPythonMutators(android.InitRegistrationContext)
+}
+
+func registerPythonMutators(ctx android.RegistrationContext) {
+	ctx.PreDepsMutators(RegisterPythonPreDepsMutators)
 }
 
 // Exported to support other packages using Python modules in tests.