Just report HTTP errors, no need to make tickets out of them.
Better error messages - inform that updating is disabled for SNAPSHOTs.
Throw an exception the caller can handle instead of a warning message.

This should prevent possible spam by plugins that are not aware that a 
player has either logged out, or is not injected due to a bug in
ProtocolLib.
Properly exit BlockingHashMap#get if we time out.