Motivation for changes:

Fixes #3472

Detailed changes:

• Torrent names can contain characters that are not allowed in URLs. This results in urllib.request.urlopen raising an exception when downloading a torrent file generated by the convert_magnet plugin.
• When generating the url for the entry in the convert_magnet plugin, ensure that it is quoted to avoid these issues by future consumers.

Addressed issues:

• Fixes <urlopen error [Errno 2] No such file or directory with # in filename #3472