qpid-tool should print warning when initial connection to broker fails

When I mistype brokerURL in e.g. qpid-stat, I get some error (ConnectError or AuthenticationFailure). But when I invoke qpid-tool with invalid credentials or hostname, the tool raises no exception or warning, leaving the user under the wrong assumption the tool has connected successfully.

qpid-tool should either exit or at least print out some warning message