# 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.
""" Delete an event source mapping
        ---
        operationId: 'deleteEventSourceMapping'
    """
    if not mapping_uuid:
        return jsonify({})
    mapping = delete_event_source(mapping_uuid)
    return jsonify(mapping)
@app.route('%s/functions/<function>/versions' % PATH_ROOT, methods=['POST'])
def publish_version(function):
    arn = func_arn(function)
    if arn not in arn_to_lambda:
        return not_found_error(arn)
    return jsonify(publish_new_function_version(arn))