Lambda function triggered by CloudTrail events to check for tagging, and notify the owner through SES if tagging not found

ec2TagCheck.py

import boto3

required_keys = [ "key01", "key02", "key03", "key04" ]
ses_source = 'source@maildomain.com'
ses_destination = ['somebody@domain.com']

def lambda_handler(event, context):

    if 'detail' in event and 'instance-id' in event['detail']:
        ec2_instance_id = event['detail']['instance-id']
        ec2 = boto3.resource('ec2')
        instance = ec2.Instance(ec2_instance_id)
        tags = instance.tags

        all_keys = []
        for tag in tags:
            all_keys.append(tag['Key'])

        missing=[]
        for rk in required_keys:
            if rk not in all_keys:
                missing.append(rk)

        if len(missing) > 0:
            message = 'missing keys in EC2(ID:' + ec2_instance_id + '):' + ','.join(missing)
            ses = boto3.client('ses')
            response = ses.send_email(
                Source=ses_source,
                Destination={
                    'ToAddresses': ses_destination
                },
                Message={
                    'Subject': {
                        'Data': message,
                        'Charset': 'ascii'
                    },
                    'Body': {
                        'Text': {
                            'Data': message,
                            'Charset': 'ascii'
                        },
                        'Html': {
                            'Data': message,
                            'Charset': 'ascii'
                        }
                    }
                },
                ReplyToAddresses=[
                    ses_source,
                ],
                ReturnPath=ses_source
            )

        return 'checked ' + ec2_instance_id + ', missing: ' + str(len(missing) > 0)
    else:
        return ''