Setting Custom error message with CarrierWave

Question

I have an Image uploading application running on carrierwave which restrict user from uploading image only of desired extensions 'jpg,jpeg,png' I have put in place the validation for carrierwave in my Uploader define as

def extension_white_list
  %w(jpg jpeg png)
end

Now anyone trying to upload image having extension different from the desired extension(mention above) will result in validation errors

I want to customize the Validation Error message

Right Now Error message is presented as

You are not allowed to upload "" files, allowed types: ["jpg","jpeg","png"]

Can anyone help I found this link where the guys mention how to achieve this

but it some problem

1. I18n support I dont require to translate the error message using I18n 

2. The 'Key' to be used I not sure which key to used in YAML for
    not matching extension whitelist error message (e.g) carrierwave_processing_error key if error is for processing failure

Please Provide me answer in term of CarrierWave and please dont ask me to write separate validation set for extension matching

Answer 1

Actually it is:

en:
  errors:
    messages:
      extension_white_list_error: "You are not allowed to upload %{extension} files, allowed types: %{allowed_types}"

Source:

https://github.com/jnicklas/carrierwave/blob/master/lib/carrierwave/locale/en.yml