Updated the patch to address the 'why not use .strip()' question. I used .rstrip('\r\n') on the basis that filenames may have leading or trailing spaces, and if you need that, you need to be able to specify that in a MANIFEST, but it is perfectly logical to disallow them, so here's a patch that doesn't support them.

It also reduces the line count by 2 because I'm composing the 'comment' and 'blank line' cases.