Fix compatibility with Ruby 2.7

Closes #206

Author: silug

lib/rspec-puppet-facts.rb

@@ -397,7 +397,7 @@ def self.facter_version_for_puppet_version(puppet_version)
       return Facter.version
     end
 
-    version_map = JSON.load_file(json_path).map do |puppet, facter|
+    version_map = JSON.parse(File.read(json_path)).map do |puppet, facter|
       [Gem::Version.new(puppet), facter]
     end
 

spec/rspec_puppet_facts_spec.rb

@@ -60,7 +60,7 @@
 
     context 'when the component JSON file is unparseable' do
       before do
-        allow(JSON).to receive(:load_file).with(component_json_path).and_raise(JSON::ParserError)
+        allow(File).to receive(:read).with(component_json_path).and_return('not json')
         allow(described_class).to receive(:warning)
       end