add check for puppet 4

Gemfile

@@ -1,33 +1,34 @@
-source ENV['GEM_SOURCE'] || 'https://rubygems.org'
+source "https://rubygems.org"
 
-group :development, :unit_tests do
-  gem 'rspec-core', '~> 3.1.7',  :require => false
-  gem 'rspec-puppet', '~> 2.1',  :require => false
-  gem 'puppetlabs_spec_helper',  :require => false
-  gem 'simplecov',               :require => false
-  gem 'puppet_facts',            :require => false
-  gem 'json',                    :require => false
-  gem 'metadata-json-lint',      :require => false
-  gem 'puppet-lint', '< 1.1.0',  :require => false
+group :test do
+  gem "rake"
+  gem "puppet", ENV['PUPPET_GEM_VERSION'] || '~> 3.8.0'
+  gem "rspec", '< 3.2.0'
+  gem "rspec-puppet", :git => 'https://github.com/rodjek/rspec-puppet.git'
+  gem "puppetlabs_spec_helper"
+  gem "metadata-json-lint"
+  gem "rspec-puppet-facts"
+  gem 'rubocop', '0.33.0'
+  gem 'simplecov', '>= 0.11.0'
+  gem 'simplecov-console'
+
+  gem "puppet-lint-absolute_classname-check"
+  gem "puppet-lint-leading_zero-check"
+  gem "puppet-lint-trailing_comma-check"
+  gem "puppet-lint-version_comparison-check"
+  gem "puppet-lint-classes_and_types_beginning_with_digits-check"
+  gem "puppet-lint-unquoted_string-check"
+end
+
+group :development do
+  gem "travis"
+  gem "travis-lint"
+  gem "puppet-blacksmith"
+  gem "guard-rake"
 end
 
 group :system_tests do
-  gem 'beaker-rspec',                  :require => false
-  gem 'serverspec',                    :require => false
-  gem 'beaker-puppet_install_helper',  :require => false
+  gem "beaker"
+  gem "beaker-rspec"
+  gem "beaker-puppet_install_helper"
 end
-
-if facterversion = ENV['FACTER_GEM_VERSION']
-  gem 'facter', facterversion, :require => false
-else
-  gem 'facter', :require => false
-end
-
-if puppetversion = ENV['PUPPET_GEM_VERSION']
-  gem 'puppet', puppetversion, :require => false
-else
-  gem 'puppet', :require => false
-end
-
-gem 'puppet', "3.8"
-# vim:ft=ruby

manifests/init.pp

@@ -13,6 +13,9 @@ class rsnapshot (
   $package_name                  = $rsnapshot::params::package_name,
   $package_ensure                = $rsnapshot::params::package_ensure,
 ) inherits rsnapshot::params {
+  if $::puppetversion =~ /^(1|2|3)/ {
+    fail("This module requires Puppet 4")
+  }
   if $hosts {
     class { 'rsnapshot::install': }->
     class { 'rsnapshot::config': }