Merge pull request cosmicpython#323 from zhangcheng/patch-1

Just to be consistent with previous cases

Author: hjwp

chapter_04_service_layer.asciidoc

@@ -550,9 +550,9 @@ def allocate_endpoint():
     try:
         batchref = services.allocate(line, repo, session)  #<2>
     except (model.OutOfStock, services.InvalidSku) as e:
-        return {"message": str(e)}, 400  <3>
+        return {"message": str(e)}, 400  #<3>
 
-    return {"batchref": batchref}, 201  <3>
+    return {"batchref": batchref}, 201  #<3>
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