Add external/python/* in root.bp

Bug: b/38395161
Test: mma under external/python/cpython2

Change-Id: I95fde837025022bf0f6b65246ab0a35a0b41972c
diff --git a/root.bp b/root.bp
index 582552e..31a95fd 100644
--- a/root.bp
+++ b/root.bp
@@ -18,6 +18,7 @@
     "development/*",
     "device/*/*",
     "external/*",
+    "external/python/*",
     "frameworks/*",
     "frameworks/compile/*",
     "frameworks/hardware/interfaces",