Here's a slightly modified version of urischeme.py that can be run under Python 3 and compares its results with urllib.parse, printing out the mismatches.

The major differences seem to be 1) urischeme fills in the default port if it's not explicitly provided, e.g. http urls have the port set to 80, 2) the path is returned as '/', not the empty string, for the URL http://host, 3) urllib.parse.urljoin() doesn't get rid of ./ and ../ in URLs.

3) seems like something worth fixing in urllib.parse.  The others probably present some backward-compatibility issues.