«Host key verification failed» means that the host key of the remote host was changed.
SSH stores the host keys of the remote hosts in ~/.ssh/known_hosts. You can either edit that text file manually and remove the old key (you can see the line number in the error message), or use
ssh-keygen -R hostname
From man page:
-R hostname
Removes all keys belonging to hostname from a known_hosts file. This option is useful to delete hashed hosts .