title: Custom Authorizer not working when used with AWS Chalice
body: <p>I am using AWS Custom Authorizer to secure lambda function. I am not able to use the custom authorizer because of some configurational issues.</p>
  
  <p>when I tried attaching the authorizer from API Gateway Console, it is working fine. When the authorizer is attached from code, it is not giving any error. I tried checking the cloudwatch logs, the logs are not generated for lambda functions(both for authorizer and helloworld function).</p>
  
  <p>Below is a sample code which I have written:</p>
  
  <pre><code>from chalice import Chalice
  from chalice import CustomAuthorizer
  app = Chalice(app_name='helloworld-python')
  
  authorizer = CustomAuthorizer(
      'MyCustomAuth', header='Authorization',
      authorizer_uri=('arn:aws:apigateway:{region}:lambda:path/2015-03-31'
                      '/functions/arn:aws:lambda:{region}:{account-id}:'
                      'function:{function-name}/invocations'))
  
  @app.route('/test/test_authorizer', authorizer=authorizer)
  def index():
      return {'hello': 'world'}
  </code></pre>
  
  <p>I have configured the following policy:</p>
  
  <pre><code>{
      "Version": "2012-10-17",
      "Statement": [
        {
          "Effect": "Allow",
          "Action": [
            "execute-api:Invoke"
          ],
          "Resource": [
            "*"
          ]
        }
      ]
    }
  </code></pre>
  
  <p>I am not able to add the authorizer to the lambda function. When I fire the endpoint it is giving me following error:</p>
  
  <blockquote>
    <p>End Point:
    https://{rest-api-id}.execute-api.{region}.amazonaws.com/dev/test/test_authorizer</p>
    
    <p>Http method: GET</p>
    
    <p>Error Code: 500.</p>
    
    <p>Error body: <code>{
        "message": null 
    }</code></p>
  </blockquote>
  
  <p>How can I achieve this. Please provide me with the proper intel.</p>