How can I fetch a dataset from Rosalind?

For purposes of testing my programs, I'd like to automate fetching datasets from Rosalind. For instance, take problem DNA: The sample input can be obtained easily from the HTML of that page, but actual problems are only served on demand, and require a login.

How can I write a function that takes the problem code, my account name, and my password as argument, asks Rosalind for a new dataset, and returns the contents of the received file? Can I do this with WebClient?