Puppet: install Rubygem-package on a machine without Rubygems preinstalled

On a clean Debian system - without Rubygems installed - I want to install a Rubygem package with Puppet. So the package has "gem" as package Provider.

This is my manifest so far (I kept it simple):

# test.pp
 Package { ensure => 'installed' } 
 
 package { 
   'rubygems' : 
     name => 'rubygems',
 }
 
 package {
   'libldap-ruby1.8' :
     name => 'libldap-ruby1.8',
 }
 
 package { 'libldap2-dev' : 
    name => 'libldap2-dev', 
 }
 
 package { 'libsasl2-dev' : 
   name => 'libsasl2-dev', 
 }
 
 package { 'libsasl2-modules-ldap' : 
   name => 'libsasl2-modules-ldap', 
 }
 
 # My Rubygem, with Provider type 'gem'
 package { 
   'ruby-ldap' : 
     name => 'ruby-ldap',
     provider => 'gem',
 }
 
 Package [ 'rubygems' ] -> Package [ 'ruby-ldap' ] 
 Package [ 'libldap2-dev' ] -> Package [ 'ruby-ldap' ]
 Package [ 'libsasl2-modules-ldap' ] -> Package [ 'ruby-ldap' ]
 

When I test this manifest (with puppet apply --noop test.pp), I'm getting the following output:

err: /Stage[main]//Package[ruby-ldap]: Provider gem is not functional on this host
 

I digged through the net and found some informations about Puppet+Rubygems (for example this) but none of these helped me to solve my problem as none provided a real solution with some code.

I also tried using classes and stages (doing the rubygem install in a stage before the gem install) but I always got the Provider gem-error (but maybe I just used the stages in a wrong way).

Can anyone provide me a working manifest which installs rubygems and any rubygem on a system without Rubygems, or at least the final hints how to get there?

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