Last Friday, I created a user account and gave it shell access. I could log into it with the password. I then added a public key to its .ssh/authorized_keys file. I then was able to log in using the key.
This morning I tried to log in and I now get this from ssh:
PTY allocation request failed on channel 0
I turned on ssh's verbose mode with -vvv and the last lines before the failure are:
debug2: channel 0: request shell confirm 1
debug2: fd 3 setting TCP_NODELAY
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel_input_status_confirm: type 100 id 0
Ok, I fixed it.
I am using gitolite and made a mistake. It was restricting my login.