Merge remote-tracking branch 'akremer/patch-psych-changes'

Raised for PR puppetlabs#976

Author: halfninja

lib/puppet/provider/docker_stack/ruby.rb

@@ -14,7 +14,7 @@ def exists?
     stack_services = {}
     stack_containers = []
     resource[:compose_files].each do |file|
-      compose_file = YAML.safe_load(File.read(file), [], [], true)
+      compose_file = Puppet::Util::Yaml.safe_load(File.read(file))
       # rubocop:disable Style/StringLiterals
       containers = docker([
                             'ps',