Sublime debugger fails to launch rails server (Ruby 2.1.4 and Rails 4.2)

It runs the command:
ruby -C/Users/sauron/git/sja -r/Users/sauron/Library/Application Support/Sublime Text 3/Packages/Ruby Debugger/sublime_debug_require.rb -rbundler/setup bin/rails s

Then hangs. No rails process is started.