How can I create an Amazon S3 notification configuration for Lambda on an existing Amazon S3 bucket using AWS CloudFormation?

from __future__ import print_function
import json
import boto3
import urllib
from botocore.vendored import requests

SUCCESS = "SUCCESS"
FAILED = "FAILED"

print('Loading function')
s3 = boto3.resource('s3')

def lambda_handler(event, context):
    print("Received event: " + json.dumps(event, indent=2))
    responseData={}
    try:
        if event['RequestType'] == 'Delete':
            print("Request Type:",event['RequestType'])
            Bucket=event['ResourceProperties']['Bucket']
            delete_notification(Bucket)
            print("Sending response to custom resource after Delete")
        elif event['RequestType'] == 'Create' or event['RequestType'] == 'Update':
            print("Request Type:",event['RequestType'])
            LambdaArn=event['ResourceProperties']['LambdaArn']
            Bucket=event['ResourceProperties']['Bucket']
            add_notification(LambdaArn, Bucket)
            responseData={'Bucket':Bucket}
            print("Sending response to custom resource")
        responseStatus = 'SUCCESS'
    except Exception as e:
        print('Failed to process:', e)
        responseStatus = 'FAILURE'
        responseData = {'Failure': 'Something bad happened.'}
    send(event, context, responseStatus, responseData)

def add_notification(LambdaArn, Bucket):
    bucket_notification = s3.BucketNotification(Bucket)
    response = bucket_notification.put(
      NotificationConfiguration={
        'LambdaFunctionConfigurations': [
            {
                'LambdaFunctionArn': LambdaArn,
                'Events': [
                    's3:ObjectCreated:*'
                ]
            }
        ]
      }
    )
    print("Put request completed....")

def delete_notification(Bucket):
    bucket_notification = s3.BucketNotification(Bucket)
    response = bucket_notification.put(
      NotificationConfiguration={}
    )
    print("Delete request completed....")


def send(event, context, responseStatus, responseData, physicalResourceId=None, noEcho=False):
    responseUrl = event['ResponseURL']
    print(responseUrl)
    responseBody = {'Status': responseStatus,
                    'Reason': 'See the details in CloudWatch Log Stream: ' + context.log_stream_name,
                    'PhysicalResourceId': physicalResourceId or context.log_stream_name,
                    'StackId': event['StackId'],
                    'RequestId': event['RequestId'],
                    'LogicalResourceId': event['LogicalResourceId'],
                    'Data': responseData}
    json_responseBody = json.dumps(responseBody)
    print("Response body:\n" + json_responseBody)
    headers = {
        'content-type' : '',
        'content-length' : str(len(json_responseBody))
    }
    try:
        response = requests.put(responseUrl,
                                data=json_responseBody,
                                headers=headers)
        print("Status code: " + response.reason)
    except Exception as e:
        print("send(..) failed executing requests.put(..): " + str(e))

-> LambdaS3.zip | |-> LambdaS3.py

aws s3 cp ./LambdaS3.zip s3://awsexamplebucket1/LambdaS3.zip

AWSTemplateFormatVersion: 2010-09-09
Description: >-
  Sample template to illustrate use of existing S3 bucket as event source for
  Lambda function
Parameters:
  NotificationBucket:
    Type: String
    Description: S3 bucket which is used for Lambda event notification
  LambdaCodeBucket:
    Type: String
    Description: S3 bucket in which custom lambda code is stored
  LambdaCodeKey:
    Type: String
    Description: Zip file name in which custom lambda code is stored
    Default: LambdaS3.zip
  Lambdahandler:
    Type: String
    Description: Python file name which is packed inside the zip file
    Default: LambdaS3

Resources:
  S3NotificationLambdaFunction:
    Type: 'AWS::Lambda::Function'
    Properties:
      Code:
        ZipFile: !Join
          - |+

          - - import json
            - 'def lambda_handler(event,context):'
            - '    return ''Welcome... This is a test Lambda Function'''
      Handler: index.lambda_handler
      Role: !GetAtt LambdaIAMRole.Arn
      Runtime: python3.6
      Timeout: 5

  LambdaInvokePermission:
    Type: 'AWS::Lambda::Permission'
    Properties:
      FunctionName: !GetAtt S3NotificationLambdaFunction.Arn
      Action: 'lambda:InvokeFunction'
      Principal: s3.amazonaws.com
      SourceAccount: !Ref 'AWS::AccountId'
      SourceArn: !Sub 'arn:aws:s3:::${NotificationBucket}'

  LambdaIAMRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Principal:
              Service:
                - lambda.amazonaws.com
            Action:
              - 'sts:AssumeRole'
      Path: /
      Policies:
        - PolicyName: root
          PolicyDocument:
            Version: 2012-10-17
            Statement:
              - Effect: Allow
                Action:
                  - 's3:*'
                Resource: '*'
              - Effect: Allow
                Action:
                  - 'logs:CreateLogGroup'
                  - 'logs:CreateLogStream'
                  - 'logs:PutLogEvents'
                Resource: 'arn:aws:logs:*:*:*'

  CustomResourceLambdaFunction:
    Type: 'AWS::Lambda::Function'
    Properties:
      Handler: !Sub '${Lambdahandler}.lambda_handler'
      Role: !GetAtt LambdaIAMRole.Arn
      Code:
        S3Bucket: !Ref LambdaCodeBucket
        S3Key: !Ref LambdaCodeKey
      Runtime: python3.6
      Timeout: 50

  LambdaTrigger:
    Type: 'Custom::RouteTableLambda'
    DependsOn: LambdaInvokePermission
    Properties:
      ServiceToken: !GetAtt CustomResourceLambdaFunction.Arn
      LambdaArn: !GetAtt S3NotificationLambdaFunction.Arn
      Bucket: !Ref NotificationBucket

aws cloudformation create-stack --stack-name lambda-s3-notification --template-body file://LambdaS3.template --parameters ParameterKey=NotificationBucket,ParameterValue=existing-bucket-for-lambda-notification ParameterKey=LambdaCodeBucket,ParameterValue=awsexamplebucket1 ParameterKey=Lambdahandler,ParameterValue=LambdaS3 ParameterKey=LambdaCodeKey,ParameterValue=LambdaS3.zip --capabilities CAPABILITY_NAMED_IAM --region us-east-1