And this is how you retrieve TARGETURI:

	uri = target_uri.path

When you want to merge another path, this is the safest way to do it:

	uri = normalize_uri(uri, 'spip.php')

A writeup about this can be found here, please feel free to check it out:
https://github.com/rapid7/metasploit-framework/wiki/How-to-Send-an-HTTP-Request-Using-HTTPClient