class Sass::SyntaxError

def add_backtrace_entry(filename) # :nodoc:

:nodoc:
if applicable (defaults to "(sass)").
+filename+ should be the file in which the error occurred,
Adds a properly formatted entry to the exception's backtrace. 
def add_backtrace_entry(filename) # :nodoc:
  @sass_filename ||= filename
  self.backtrace ||= []
  self.backtrace.unshift "#{@sass_filename || '(sass)'}:#{@sass_line}"
end