When you create a Lambda permission you send the __statement id__ as mandatory parameter.

https://docs.aws.amazon.com/lambda/latest/dg/API_AddPermission.html#API_AddPermission_RequestSyntax

However this id is generated by a random value. 

https://github.com/localstack/localstack/blob/b3917bf248b77ced8ef80a3d5c0561960066db5d/localstack/services/awslambda/lambda_api.py#L927

Due to this problem, the tools like Terraform or Ansible fail when it has to be retrieved to check the existence of this element.

If you agree I could make a PR with the fix and its test.
mapping = {
        'UUID': str(uuid.uuid4()),
        'StateTransitionReason': 'User action',
        'LastModified': float(time.mktime(datetime.utcnow().timetuple())),
        'BatchSize': 100,
        'State': 'Enabled' if enabled is True or enabled is None else 'Disabled',
        'FunctionArn': func_arn(function_name),
        'EventSourceArn': source_arn,
        'LastProcessingResult': 'OK',
        'StartingPosition': LAMBDA_DEFAULT_STARTING_POSITION
    }
    event_source_mappings.append(mapping)
    return mapping
def update_event_source(uuid_value, function_name, enabled, batch_size):
    for m in event_source_mappings:
        if uuid_value == m['UUID']:
            if function_name:
                m['FunctionArn'] = func_arn(function_name)
            m['BatchSize'] = batch_size
            m['State'] = 'Enabled' if enabled is True else 'Disabled'
            m['LastModified'] = float(time.mktime(datetime.utcnow().timetuple()))
            return m
    return {}
def delete_event_source(uuid_value):