Add support for python_defaults modules

Test: python_test.go
Change-Id: I2077414a5b06da5e660a1b48bfdb2eb926fb702f
diff --git a/python/python.go b/python/python.go
index d462af1..e63c26c 100644
--- a/python/python.go
+++ b/python/python.go
@@ -109,6 +109,7 @@
 
 type Module struct {
 	android.ModuleBase
+	android.DefaultableModuleBase
 
 	properties BaseProperties
 
@@ -194,6 +195,7 @@
 	}
 
 	android.InitAndroidArchModule(p, p.hod, p.multilib)
+	android.InitDefaultableModule(p)
 
 	return p
 }