Foreman » Smart Proxy

Description of problem:
Impossible to use customrun puppet provider

Version-Release number of selected component (if applicable):
foreman-proxy-1.8.2-2.el7.noarch

How reproducible:
100%

Steps to Reproduce:
1. # cat /etc/foreman-proxy/settings.d/puppet.yml | grep customrun
:puppet_provider: customrun
:customrun_cmd: /usr/local/bin/mco
:customrun_args: -a

2. Restart foreman proxy
3. Press "Run puppet"

Actual results:
/var/log/foreman-proxy/proxy.log:
E, [2015-06-26T15:02:58.471796 #4759] ERROR -- : Exception 'no implicit conversion of Array into String' when executing '["/usr/local/bin/mco", "-a", ["host.domain.tld"]]'
E, [2015-06-26T15:02:58.474202 #4759] ERROR -- : Failed puppet run: Check Log files
IP - - [26/Jun/2015 15:02:58] "POST /puppet/run HTTP/1.1" 500 34 0.0062

Expected results:
Execute /usr/local/bin/mco -a host.domain.tld