Convert tests to use plain rspec-puppet

Tests in the new style produces the following documentation output:

abs
  should not eq nil
  should run abs() and raise an Puppet::ParseError
  should run abs(-34) and return 34
  should run abs("-34") and return 34
  should run abs(34) and return 34
  should run abs("34") and return 34

1 files changed, 6 insertions, 10 deletions

diff --git a/spec/functions/private_spec.rb b/spec/functions/private_spec.rb
index c90282e..a13be64 100644
--- a/spec/functions/private_spec.rb
+++ b/spec/functions/private_spec.rb
@@ -1,17 +1,13 @@
-#! /usr/bin/env ruby -S rspec
 require 'spec_helper'
 
-describe Puppet::Parser::Functions.function(:private) do
-  let(:scope) { PuppetlabsSpec::PuppetInternals.scope }
-
-  subject do
-    function_name = Puppet::Parser::Functions.function(:private)
-    scope.method(function_name)
-  end
-
+describe 'private' do
   it 'should issue a warning' do
     scope.expects(:warning).with("private() DEPRECATED: This function will cease to function on Puppet 4; please use assert_private() before upgrading to puppet 4 for backwards-compatibility, or migrate to the new parser's typing system.")
-    subject.call []
+    begin
+      subject.call []
+    rescue
+      # ignore this
+    end
   end
 
   context "when called from inside module" do