"bzr branch lp:lxlauncher" doesn't work

Whenever I try the command "bzr branch lp:lxlauncher", I receive this error message:

$ bzr branch lp:lxlauncher
Permission denied (publickey).
bzr: ERROR: Connection closed: Unexpected end of message. Please check connectivity and permissions, and report a bug if problems persist.

And when I tried with sudo:

$ sudo bzr branch lp:lxlauncher
The authenticity of host 'bazaar.launchpad.net (91.189.90.11)' can't be established.
RSA key fingerprint is 9d:38:3a:63:b1:d5:6f:c4:44:67:53:49:2e:ee:fc:89.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'bazaar.launchpad.net,91.189.90.11' (RSA) to the list of known hosts.
Permission denied (publickey).
bzr: ERROR: Connection closed: Unexpected end of message. Please check connectivity and permissions, and report a bug if problems persist.

Now with or without sudo I receive always the same first error message.