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
LOCALSTACK_VENV_FOLDER = os.path.join(LOCALSTACK_ROOT_FOLDER, '.venv')
if not os.path.isdir(LOCALSTACK_VENV_FOLDER):
    
    LOCALSTACK_VENV_FOLDER = os.path.realpath(os.path.join(LOCALSTACK_ROOT_FOLDER, '..', '..', '..'))
PATH_USER_REQUEST = '_user_request_'
DOCKER_IMAGE_NAME = 'localstack/localstack'
CONFIG_UPDATE_PATH = '/?_config_'
ENV_INTERNAL_TEST_RUN = 'LOCALSTACK_INTERNAL_TEST_RUN'
APPLICATION_AMZ_JSON_1_0 = 'application/x-amz-json-1.0'
APPLICATION_AMZ_JSON_1_1 = 'application/x-amz-json-1.1'
APPLICATION_JSON = 'application/json'
APPLICATION_X_WWW_FORM_URLENCODED = 'application/x-www-form-urlencoded'
TRUE_STRINGS = ('1', 'true', 'True')
FALSE_STRINGS = ('0', 'false', 'False')
LAMBDA_TEST_ROLE = 'arn:aws:iam::%s:role/lambda-test-role' % TEST_AWS_ACCOUNT_ID
ELASTICSEARCH_JAR_URL = 'https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.7.0.zip'
ELASTICSEARCH_PLUGIN_LIST = ['analysis-icu', 'ingest-attachment', 'analysis-kuromoji',
 'mapper-murmur3', 'mapper-size', 'analysis-phonetic', 'analysis-smartcn', 'analysis-stempel', 'analysis-ukrainian']
ELASTICSEARCH_DELETE_MODULES = ['ingest-geoip']
ELASTICMQ_JAR_URL = 'https://s3-eu-west-1.amazonaws.com/softwaremill-public/elasticmq-server-0.15.2.jar'
STS_JAR_URL = 'https://repo1.maven.org/maven2/com/amazonaws/aws-java-sdk-sts/1.11.14/aws-java-sdk-sts-1.11.14.jar'
STEPFUNCTIONS_ZIP_URL = 'https://s3.amazonaws.com/stepfunctionslocal/StepFunctionsLocal.zip'
DYNAMODB_JAR_URL_ALPINE = 'https://github.com/whummer/dynamodb-local/raw/master/etc/DynamoDBLocal.zip'
DYNAMODB_JAR_URL = 'https://s3-us-west-2.amazonaws.com/dynamodb-local/dynamodb_local_latest.zip'
API_ENDPOINT = os.environ.get('API_ENDPOINT') or 'https://api.localstack.cloud/v1'
LOCALSTACK_WEB_PROCESS = 'LOCALSTACK_WEB_PROCESS'
LOCALSTACK_INFRA_PROCESS = 'LOCALSTACK_INFRA_PROCESS'
MOTO_ACCOUNT_ID = '123456789012'
DEFAULT_LAMBDA_CONTAINER_REGISTRY = 'lambci/lambda'