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.
}]
    }
    iam_client.create_policy(PolicyName=POLICY_NAME_PATTERN % function,
        PolicyDocument=json.dumps(policy), Description='Policy for Lambda function "%s"' % function)
    result = {'Statement': sid}
    return jsonify(result)
@app.route('%s/functions/<function>/policy/<statement>' % PATH_ROOT, methods=['DELETE'])
def remove_permission(function, statement):
    qualifier = request.args.get('Qualifier')
    iam_client = aws_stack.connect_to_service('iam')
    policy = get_lambda_policy(function)
    if not policy:
        return error_response('Unable to find policy for Lambda function "%s"' % function,
            404, error_type='ResourceNotFoundException')
    iam_client.delete_policy(PolicyArn=policy['PolicyArn'])
    result = {
        'FunctionName': function,
        'Qualifier': qualifier,
        'StatementId': policy['Statement'][0]['Sid'],
    }
    return jsonify(result)
@app.route('%s/functions/<function>/policy' % PATH_ROOT, methods=['GET'])
def get_policy(function):
    policy = get_lambda_policy(function)
    if not policy:
        return jsonify({}), 404
    return jsonify({'Policy': json.dumps(policy), 'RevisionId': 'test1234'})
@app.route('%s/functions/<function>/invocations' % PATH_ROOT, methods=['POST'])
def invoke_function(function):
    """ Invoke an existing function