config-custom.yaml not loading on vagrant / puppet VM

Question

I'm trying to use a custom config file in my vagrant machine.

I have all the main params in the puphpet\config.yaml and the local overrides in puppet\config-custom.yaml

I couldn't get the file to load so after much searching i figured i needed to change the vagrant file

so i added

configValues = YAML.load_file("#{dir}/puphpet/config.yaml")

if File.file?("#{dir}/puphpet/config-custom.yaml")
  custom = YAML.load_file("#{dir}/puphpet/config-custom.yaml")
  configValues.deep_merge(custom)
end

data = configValues['vagrantfile-local']

but this just gives me

Message: NoMethodError: undefined method `deep_merge' for #<Hash:0x00000101b6bac8>

originally the code said

 configValues.deep_merge!(custom)

But that did not work either,