It is my understanding that setting an environment varialbe `TEST_AWS_ACCOUNT_ID` for localstack sets that as the AWS account for the user in localstack.

However, setting it does not actually change any ARNs. For example:

1. Start localstack using `TEST_AWS_ACCOUNT_ID="111111111111" DEBUG=1 localstack start`
2. Deploy anything with an ARN (in this example I deployed a lambda)
3. Check the ARN. Example output for lambda:
```json
$ awslocal lambda list-functions
{
    "Functions": [
        {
            "FunctionName": "localtest-local-hello",
            "FunctionArn": "arn:aws:lambda:us-east-1:000000000000:function:localtest-local-hello",
            "Runtime": "nodejs10.x",
            "Role": "test_role",
            "Handler": "handler.hello",
            "CodeSize": 3077,
            "Description": "",
            "Timeout": 6,
            "MemorySize": 1024,
            "LastModified": "2019-11-06T06:43:53.451+0000",
            "CodeSha256": "V77gR13o90ET7+XquXBBc3Rxr1qDu1bE7S+A0Wbx5ys=",
            "Version": "$LATEST",
            "TracingConfig": {
                "Mode": "PassThrough"
            },
            "RevisionId": "3d4ed679-c1a9-4b7e-ad9e-f27e8543c5e9"
        }
    ]
}
```

ARN is still 000000000000
import os
import localstack_client.config
VERSION = '0.10.4'
REGION_LOCAL = 'local'
ENV_DEV = 'dev'
DEFAULT_PORT_APIGATEWAY_BACKEND = 4566
DEFAULT_PORT_KINESIS_BACKEND = 4565
DEFAULT_PORT_DYNAMODB_BACKEND = 4564
DEFAULT_PORT_S3_BACKEND = 4563
DEFAULT_PORT_SNS_BACKEND = 4562
DEFAULT_PORT_SQS_BACKEND = 4561
DEFAULT_PORT_ELASTICSEARCH_BACKEND = 4560
DEFAULT_PORT_CLOUDFORMATION_BACKEND = 4559
DEFAULT_PORT_STEPFUNCTIONS_BACKEND = 4558
DEFAULT_PORT_IAM_BACKEND = 4557
DEFAULT_PORT_EC2_BACKEND = 4556
DEFAULT_PORT_WEB_UI = 8080
LOCALHOST = 'localhost'
LOCALSTACK_MAVEN_VERSION = '0.1.22'
DEFAULT_SERVICE_PORTS = localstack_client.config.get_service_ports()
BIND_HOST = '0.0.0.0'
if 'TEST_AWS_ACCOUNT_ID' not in os.environ:
    os.environ['TEST_AWS_ACCOUNT_ID'] = '000000000000'
TEST_AWS_ACCOUNT_ID = os.environ['TEST_AWS_ACCOUNT_ID']
LOCALSTACK_ROOT_FOLDER = os.path.realpath(os.path.join(os.path.dirname(os.path.realpath(__file__)), '..'))