My 6.x-4.6 cart had been working fine until I added Shipping API and the UPS modules. Now, I get a WSOD:

Fatal error: Call to undefined function ec_devel_prettyxml() in /home/username/domain.com/devsite/sites/all/modules/ec_ups/ec_ups.module on line 227

I searched the boards for answers and found none. Any idea what's going on?