Issue 3996 - Make sure to install current versions of Markdown and Jinja2 modules on web servers

modules/web/manifests/server.pp

 class web::server(
     $vhost,
     $repository,
     $certificate = hiera('web::server::certificate', 'undef'),
     $private_key = hiera('web::server::private_key', 'undef'),
     $is_default = false,
     $aliases = undef,
     $custom_config = undef,
     $multiplexer_locations = undef,
     $geoip = false,
@@ skipping 23 matching lines @@
       false => undef,
       default => '/usr/share/GeoIP/GeoIPv6.dat',
     },
   }
 
   class {'geoip':
     cron => {hour => 0, minute => 8, monthday => 15},
     ensure => $geoip ? {false => 'absent', default => 'present'},
   }
 
-  package {['python-jinja2', 'python-markdown']:}
+  ensure_packages(['python-pip'])
+
+  # Make sure that apt packages corresponding to the pip-installed modules below
+  # won't be installed unintentionally, these will take precedence otherwise.
+  package {['python-jinja2', 'python-markdown']:
+    ensure => 'held',
+  }
+
+  package {'Jinja2':
+    ensure => '2.8',
+    provider => 'pip',
+    require => [Package['python-pip'], Package['python-jinja2']],
+  }
+
+  package {'markdown':
+    ensure => '2.6.6',
+    provider => 'pip',
+    require => [Package['python-pip'], Package['python-markdown']],
+  }
 
   nginx::hostconfig {$vhost:
     content => template('web/site.conf.erb'),
     global_config => template('web/global.conf.erb'),
     is_default => $is_default,
     certificate => $certificate ? {'undef' => undef, default => $certificate},
     private_key => $private_key ? {'undef' => undef, default => $private_key},
     log => "access_log_$vhost"
   }
 
@@ skipping 102 matching lines @@
       Class['sitescripts'],
       Exec['install_jsdoc'],
       Package['make', 'doxygen'],
       File['/var/www/docs'],
     ],
     command => 'python -m sitescripts.docs.bin.generate_docs',
     user => www,
     minute => '5-55/10',
   }
 }