Use ParseError that is auto-generated by KPeg

Author: aycabta

lib/rdoc/markdown.kpeg

@@ -349,7 +349,7 @@
   # with the linking `text` (usually whitespace).
 
   def link_to content, label = content, text = nil
-    raise 'enable notes extension' if
+    raise ParseError, 'enable notes extension' if
       content.start_with? '^' and label.equal? content
 
     if ref = @references[label] then

test/test_rdoc_markdown.rb

@@ -717,7 +717,7 @@ def test_parse_note_inline
   def test_parse_note_no_notes
     @parser.notes = false
 
-    assert_raises RuntimeError do # TODO use a real error
+    assert_raises RDoc::Markdown::ParseError do
       parse "Some text.[^1]"
     end
   end