Puppet users - Dec 2013 - Debugging execution error with vcsrepo

I'm using the vcsrepo module to clone a git repo as a particular user, and 
I'm getting a puzzling error:

Debug: Executing '/usr/bin/su myuser -c "/usr/local/bin/git clone 
git@git.myhostname.com:repos/myrepo.git /home/myuser/myrepo"'
Error: Execution of '/usr/bin/su myuser -c "/usr/local/bin/git clone 
git@git.myhostname.com:repos/myrepo.git /home/myuser/myrepo"' returned
127:
su: /usr/local/bin/git clone git@git.myhostname.com:repos/myrepo.git 
/home/myuser/myrepo: No such file or directory

When I copy and paste the exact command and run it, it works fine. I can't 
figure out what would be complaining about "No such file or
directory".
Every executable and path mentioned in the command exists. 

My relevant classes look like this:

class sshd {
  file { "/etc/ssh/sshd_config":
    source => "puppet:///modules/sshd/sshd_config",
    notify => Service["sshd"]
  }

  file { "/etc/ssh/ssh_config":
    source => "puppet:///modules/sshd/ssh_config",
    notify => Service["sshd"]
  }

  service { "sshd":
    ensure => "running",
  }
}

class myuser {
  file { "/home/myuser/.ssh":
    ensure => "directory",
    mode   => "0700",
    owner  => "myuser",
    group  => "myuser",
  }

  file { "/home/myuser/.ssh/known_hosts":
    source => "puppet:///modules/myuser/.ssh/known_hosts",
    owner  => "myuser",
    group  => "myuser",
  }

  file { "/home/myuser/.ssh/id_rsa":
    source => "puppet:///modules/myuser/.ssh/id_rsa",
    mode   => "0600",
    owner  => "myuser",
    group  => "myuser",
  }

  vcsrepo { "/home/myuser/myrepo":
    require  => Class["sshd"],
    ensure   => present,
    provider => git,
    source   => 'git@git.myhostname.com:repos/myrepo.git',
    revision => 'master',
    user     => 'myuser'
  }
}

Any pointers?

-- 
You received this message because you are subscribed to the Google Groups
"Puppet Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to puppet-users+unsubscribe@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/puppet-users/e0dbbc3b-1377-4b3b-8e04-76aebfa26e38%40googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.