烧瓶瓶塞请求后触发错误

我有一个API Flask 和 Flask-Restplus . 我的文件 api.py 包含以下内容:

from flask import Flask, request, Blueprint, abort, jsonify, url_for
from flask_cors import CORS
from flask_restplus import Resource, Api, fields
[...]

app = Flask(__name__)
CORS(app)

# Create blue print to indicate api base url
blueprint = Blueprint('api', __name__, url_prefix='/cs/api')
api = Api(
    blueprint,
    title='My API',
    version='v1',
    description='Some description',
    doc='/doc',
    contact='my@email.com')
Api.specs_url = specs_url
app.register_blueprint(blueprint)

# All endpoints are defined here and work fine
[...]

@app.after_request
def audit_trail(response):
    if request.method != 'OPTIONS':
        # Do stuff
        [...]
        print('Bye')
    return True

我的API以前工作得很好,但是自从我添加了 @app.after_request 布洛克 Flask-CORS 为所有HTTP请求触发以下错误消息的包:

if resp.headers.get(acl源站):

attributeError:“bool”对象没有属性“headers”

请参见下面的跟踪:

Bye
[2018-05-23 19:03:00,468] ERROR in app: Exception on /cs/api/doc [GET]
Traceback (most recent call last):
  File "/home/alexis/Conda/envs/cs/lib/python3.5/site-packages/flask/app.py", line 1988, in wsgi_app
    response = self.full_dispatch_request()
  File "/home/alexis/Conda/envs/cs/lib/python3.5/site-packages/flask/app.py", line 1643, in full_dispatch_request
    response = self.process_response(response)
  File "/home/alexis/Conda/envs/cs/lib/python3.5/site-packages/flask/app.py", line 1862, in process_response
    response = handler(response)
  File "/home/alexis/Conda/envs/cs/lib/python3.5/site-packages/flask_cors/extension.py", line 167, in cors_after_request
    if resp.headers.get(ACL_ORIGIN):
AttributeError: 'bool' object has no attribute 'headers'

知道为什么以及如何修复它吗?