Certain attributes are required on specific tags in an RSS feed. If a feed is missing one of these attributes, a MissingAttributeError is raised.

Methods
N
Attributes
[R] attribute
[R] tag
Class Public methods
new(tag, attribute)

Source: show | on GitHub 

# File lib/rss/rss.rb, line 123
def initialize(tag, attribute)
  @tag, @attribute = tag, attribute
  super("attribute <#{attribute}> is missing in tag <#{tag}>")
end