run_tests --debug doesn't work anymore

root@dev1:~# run_tests --debug --test Soledad/Is_Soledad_running?
/usr/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- debugger (LoadError)
	from /usr/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
	from /srv/leap/bin/run_tests:510:in `'

(from redmine: created on 2016-10-06)