# Steps to reproduce

* Start `localstack` (version 0.10.3).
* Don't create any lambda functions.
* Run:

```sh
AWS_ACCESS_KEY_ID='a' AWS_SECRET_ACCESS_KEY='b' \
aws lambda invoke \
  --function-name 'my-func' \
  --qualifier='qual' \
  --endpoint http://localhost:4574 test.out
```

* Expected behaviour — a `ResourceNotFoundException` from `aws-cli`.
* Actual behaviour — `An error occurred (500) when calling the Invoke operation` message and a 500 response.

This bug only appears if a `qualifier` is included in the request.
if runtime.startswith(LAMBDA_RUNTIME_DOTNETCORE2) or runtime.startswith(LAMBDA_RUNTIME_DOTNETCORE21):
        return handler_name.split(':')[-1]
    else:
        return handler_name.split('.')[-1]
def error_response(msg, code=500, error_type='InternalFailure'):
    LOG.warning(msg)
    return aws_responses.flask_error_response(msg, code=code, error_type=error_type)
def get_zip_bytes(function_code):
    """Returns the ZIP file contents from a FunctionCode dict.
    :type function_code: dict
    :param function_code: https://docs.aws.amazon.com/lambda/latest/dg/API_FunctionCode.html
    :returns: bytes of the Zip file.
    """
    if 'S3Bucket' in function_code:
        s3_client = aws_stack.connect_to_service('s3')