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
""" Returns True if host responds to a ping request """
    is_windows = platform.system().lower() == 'windows'
    ping_opts = '-n 1' if is_windows else '-c 1'
    args = 'ping %s %s' % (ping_opts, host)
    return subprocess.call(args, shell=not is_windows, stdout=subprocess.PIPE, stderr=subprocess.PIPE) == 0
def in_docker():
    """ Returns True if running in a docker container, else False """
    if not os.path.exists('/proc/1/cgroup'):
        return False
    with open('/proc/1/cgroup', 'rt') as ifh:
        return 'docker' in ifh.read()
is_in_docker = in_docker()