add macros to flat graph (#332)

automatic commit by git-black, original commits:
  de06d65

core/dbt/exceptions.py

@@ -657,7 +657,7 @@ def dependency_not_found(model, target_model_name):
 def macro_not_found(model, target_macro_id):
     raise_compiler_error(
         model,
-        "'{}' references macro '{}' which is not defined!"
+        "'{}' references macro '{}' which is not defined!".format(
             model.unique_id, target_macro_id
         ),
     )