The endpoint requires basic auth, which I have attempted to pass by using InvokeHTTP's digest auth, as well as passing the string in a flowfile, and I also tried base64 encoding the string. But all returned 401 errors. I had a similar issue with basic auth when trying to connect to a GNIP stream.
I also tried with a GetHTTP processor, however this returned a 403 error.
I can pull the data with the following python code.