class I18n::ExceptionHandler

Note that the exception handler is not called when the option :raise was given.
was caught the handler returns an error message string containing the key/scope.
MissingTranslationData exceptions are re-raised. When a MissingTranslationData
Handles exceptions raised in the backend. All exceptions except for

def call(exception, locale, key, options) 

def call(exception, locale, key, options)
  if exception.is_a?(MissingTranslationData)
    #
    # TODO: this block is to be replaced by `exception.message` when
    # rescue_format is removed
    if options[:rescue_format] == :html
      if @rescue_format_deprecation
        $stderr.puts "[DEPRECATED] I18n's :recue_format option will be removed from a future release. All exception messages will be plain text. If you need the exception handler to return an html format please set or pass a custom exception handler."
        @rescue_format_deprecation = true
      end
      exception.html_message
    else
      exception.message
    end
  else
    raise exception
  end
end