Tuleap currently uses HTMLPurifier with a version locked on a specific commit. This has been done to work around the issue described in request #11578.
With our recent move to the remi-safe SCL (request #12067) we can use a released version again, both constants IDNA_NONTRANSITIONAL_TO_ASCII and INTL_IDNA_VARIANT_UTS46 are now properly defined.