Customising Rails error header message

It turns out that it is very easy to customise the error message header.
Goto config/locales
open up en.yaml and paste the following into it

"en":
  activerecord:
    errors:
      template:
        header:
          one:    "{{model}} is not valid"
          other:  "There are {{count}} errors prohibiting this {{model}} from being saved"
        # The variable :count is also available
        body: "The following fields have problems:"

Edit the text as you require and save the file.

That's it