The release notes for py2exe 0.6.9 (from 3 whole years ago) say that this version adds a feature to allow you to specify the necessary Windows Vista User Access Control level for your application. Indeed, this feature does exist. The release notes call the flag to utilize this feature uac_execution_info. The release notes are also the only place in the entire source tree where this string exists.
The flag is actually called uac_info.