class DeviseTokenAuthEmailValidator

def email_invalid_message
  # Try strictly set message:
  message = options[:message]
  if message.nil?
    # Try DeviceTokenAuth translations or fallback to ActiveModel translations
    message = I18n.t(:'errors.messages.not_email', default: :'errors.messages.invalid')
  end
  message
end

def validate_each(record, attribute, value)
  unless value =~ /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\z/i
    record.errors.add(attribute, email_invalid_message)
  end
end