insufficientPermissions

I am trying to insert a new post at my blogger account from app script; 
script seem to work fine, it's getting token however here is what it's 
showing:

{
 "error": {
  "errors": [
   {
    "domain": "global",
    "reason": "insufficientPermissions",
    "message": "Insufficient Permission"
   }
  ],
  "code": 403,
  "message": "Insufficient Permission"
 }
}

I know this question is asked multiple times however most of them are too 
old and Google has revised a lot of things.

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