Really! A password is being awaited - but somehow the prompt has got obfuscated by the curl stuff. If I press return, I get told the password is wrong and then prompted again (and if I supply the correct password - at this point or, by mystical intuition, earlier - all is dandy.) Can the command be modified so as to solve the problem.
EDIT: the curl command is recommended here, and it is my preferred way - apart from the problem - to install. And I don't fancy doing su beforehand, and indeed I think there might be another post about a problem with doing that.
That hides the output from curl and you just see the password prompt. Not sure if that flag is consistent on every Linux flavor but I'd feel pretty good about that change as it's a bit cleaner.
I think for simplicity in my head, the -s is easy enough as it's not a huge thing it's download so progress on a file that takes less than a second or two doesn't add much.
Generally if you are curl | bash'ing something, there is an assumption that the source is trusted/good so not seeing the output doesn't seem like a big deal.