Use symbols for the facter_implementation setting

Author: GabrielNagy

lib/rspec-puppet.rb

@@ -43,7 +43,7 @@ def self.current_example
   c.add_setting :default_node_params, :default => {}
   c.add_setting :default_trusted_facts, :default => {}
   c.add_setting :default_trusted_external_data, :default => {}
-  c.add_setting :facter_implementation, :default => 'facter'
+  c.add_setting :facter_implementation, :default => :facter
   c.add_setting :hiera_config, :default => Puppet::Util::Platform.actually_windows? ? 'c:/nul/' : '/dev/null'
   c.add_setting :parser, :default => 'current'
   c.add_setting :trusted_node_data, :default => false

lib/rspec-puppet/adapters.rb

@@ -247,7 +247,7 @@ def setup_puppet(example_group)
             Puppet.runtime[:facter] = FacterImpl
           else
             warn "Facter runtime implementations are not supported in Puppet #{Puppet.version}, continuing with facter_implementation 'facter'"
-            RSpec.configuration.facter_implementation = 'facter'
+            RSpec.configuration.facter_implementation = :facter
             set_facter_impl(Facter)
           end
         when :facter