old_contents: class CashewException(Exception):
      pass
  
  class InternalCashewException(CashewException):
      pass
  
  class UserFeedback(CashewException):
      pass
  
  class InactivePlugin(UserFeedback):
      def __init__(self, plugin_instance_or_alias):
          if isinstance(plugin_instance_or_alias, basestring):
              self.message = plugin_instance_or_alias
          else:
              self.message = plugin_instance_or_alias.alias
  
  class NoPlugin(UserFeedback):
      pass
  
new_contents: class CashewException(Exception):
      pass
  
  class InternalCashewException(CashewException):
      pass
  
  class UserFeedback(CashewException):
      pass
  
  class InactivePlugin(UserFeedback):
      def __init__(self, plugin_instance_or_alias):
          if isinstance(plugin_instance_or_alias, basestring):
              self.alias = plugin_instance_or_alias
          else:
              self.alias = plugin_instance_or_alias.alias
  
      def __str__(self):
          return "%s is inactive. Some additional software might need to be installed." % (self.alias)
  
  class NoPlugin(UserFeedback):
      pass
  
subject: Improve error message when alias not available.