leap_android does not warn about connection refused errors
Now that bitmask.net is down, I've seen that the message shown to the user is that "the provider url is not a leap provider url".
It's false: it's only that it's down.
A way to check that it's actually a leap provider url is (given the bitmask.net example) to see if provider.json was correctly downloaded.
(from redmine: created on 2013-04-22, closed on 2013-05-15)