docstr: Test that HTTPException's headers do not add a duplicate
  Content-Length header
  
  https://github.com/flask-restful/flask-restful/issues/534
docstr_tok: ["Test","that","HTTPException","'s","headers","do","not","add","a","duplicate","Content-Length","header","https",":","\/\/github.com\/flask-restful\/flask-restful\/issues\/534"]
code: def test_exception_header_forwarding_doesnt_duplicate_headers(
      self, api
  ):
      """Test that HTTPException's headers do not add a duplicate
      Content-Length header
  
      https://github.com/flask-restful/flask-restful/issues/534
      """
      r = api.handle_error(BadRequest())
      assert len(r.headers.getlist("Content-Length")) == 1
  
imports: from __future__ import unicode_literals
  import flask
  import pytest
  import six
  from json import dumps, JSONEncoder
  from flask import Blueprint, redirect, views
  from werkzeug.exceptions import HTTPException, Unauthorized, BadRequest
  import flask_restplus
label_desc: Use image node_id 33 for calling the APITest obj's underlying member method code with example usage: obj.test_exception_header_forwarding_doesnt_duplicate_headers(api) without return types