diff --git a/tools/buildgen/bunch.py b/tools/buildgen/bunch.py
index 0ce9a6b..f3bfc81 100755
--- a/tools/buildgen/bunch.py
+++ b/tools/buildgen/bunch.py
@@ -48,5 +48,6 @@
     elif isinstance(dst, list) and isinstance(add, list):
         dst.extend(add)
     else:
-        raise Exception('Tried to merge incompatible objects %s %s\n\n%r\n\n%r'
-                        % (type(dst).__name__, type(add).__name__, dst, add))
+        raise Exception(
+            'Tried to merge incompatible objects %s %s\n\n%r\n\n%r' %
+            (type(dst).__name__, type(add).__name__, dst, add))