Sjoerd Mullender writes:

Urllib makes the URL of the opened file available through the geturl
method of the returned object.  For local files, this consists of
file: plus the name of the file.  This results in an invalid URL if
the file name was relative.  This patch fixes this so that the
returned URL is just a relative URL in that case.  When the file name
is absolute, the URL returned is of the form file:///absolute/path.

[I guess that a URL of the form "file:foo.html" is illegal...  GvR]