Issue 4491 - Adds handling for block commented page metadata

cms/converters.py

 # This file is part of the Adblock Plus web scripts,
 # Copyright (C) 2006-2017 eyeo GmbH
 #
 # Adblock Plus is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 3 as
 # published by the Free Software Foundation.
 #
 # Adblock Plus is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@@ skipping 104 matching lines @@
 
     def handle_charref(self, name):
         self._append_text(self.unescape('&#{};'.format(name)))
 
 
 def parse_page_content(page, data):
     """Separate page content into metadata (dict) and body text (str)"""
     page_data = {'page': page}
     lines = data.splitlines(True)
     for i, line in enumerate(lines):
+        if line.strip() in {'<!--', '-->'}:
+            lines[i] = ''
+            continue
         if not re.search(r'^\s*[\w\-]+\s*=', line):
             break
         name, value = line.split('=', 1)
         value = value.strip()
         if value.startswith('[') and value.endswith(']'):
             value = [element.strip() for element in value[1:-1].split(',')]
         lines[i] = '\n'
         page_data[name.strip()] = value
     return page_data, ''.join(lines)
 
@@ skipping 418 matching lines @@
                 stack.pop()
             stack[-1]['subitems'].append(item)
             stack.append(item)
         return structured
 
 converters = {
     'html': RawConverter,
     'md': MarkdownConverter,
     'tmpl': TemplateConverter,
 }