The USE="xml" flag is available only starting from dev-lang/python-2.5.4-r2 Which means if you only unmask html5lib, it will refuse to be installed, whereas it could work perfectly with the stable python package. Solutions (they both suck): - remove the [xml] from the requirements - require >=dev-lang/python-2.5.4-r2[xml] - ??? Reproducible: Always
Stable python now has an xml USE flag.