capistrano: upgrading from v2.x to v3 - Net::SSH::AuthenticationFailed

I was using capistrano 2.x successfully and this morning while doing a bundle update got capistrano v3. Went through migration document and now when I run this cap production deploy --trace

I am getting:

** Invoke production (first_time)
** Execute production
** Invoke load:defaults (first_time)
** Execute load:defaults
** Invoke deploy (first_time)
** Execute deploy
** Invoke deploy:starting (first_time)
** Invoke deploy:set_shared_assets (first_time)
** Execute deploy:set_shared_assets
** Execute deploy:starting
** Invoke deploy:check (first_time)
** Execute deploy:check
** Invoke git:check (first_time)
** Invoke git:wrapper (first_time)
** Execute git:wrapper
cap aborted!
Net::SSH::AuthenticationFailed
/usr/local/lib/ruby/gems/2.0.0/gems/net-ssh-2.7.0/lib/net/ssh.rb:215:in `start'
/usr/local/lib/ruby/gems/2.0.0/gems/sshkit-0.0.34/lib/sshkit/backends/netssh.rb:156:in `ssh'
/usr/local/lib/ruby/gems/2.0.0/gems/sshkit-0.0.34/lib/sshkit/backends/netssh.rb:68:in `upload!'
/usr/local/lib/ruby/gems/2.0.0/gems/capistrano-3.0.0/lib/capistrano/tasks/git.rake:11:in `block (3 levels) in <top (required)>'
/usr/local/lib/ruby/gems/2.0.0/gems/sshkit-0.0.34/lib/sshkit/backends/netssh.rb:42:in `instance_exec'
/usr/local/lib/ruby/gems/2.0.0/gems/sshkit-0.0.34/lib/sshkit/backends/netssh.rb:42:in `run'
/usr/local/lib/ruby/gems/2.0.0/gems/sshkit-0.0.34/lib/sshkit/runners/parallel.rb:29:in `block (2 levels) in execute'
Tasks: TOP => git:check => git:wrapper

It appears that is a problem with ssh authentication / authorization – what I don’t understand is that v3 is running from the same client to the same production server where 2.x was working from

Any ideas ?