old_contents: from coalib.parsing.filters import available_filters
  
  
  class InvalidFilterException(Exception):
      def __init__(self, filter_name):
          super().__init__('{!r} is an invalid filter. Available filters: {}'
                           .format(filter_name,
                                   ', '.join(sorted(available_filters))))
  
new_contents: from coalib.parsing.filters import available_filters
  
  
  class InvalidFilterException(LookupError):
      def __init__(self, filter_name):
          super().__init__('{!r} is an invalid filter. Available filters: {}'
                           .format(filter_name,
                                   ', '.join(sorted(available_filters))))
  
subject: Change base class