Don't use URI for changing extension.

Fixes: #165
3 jobs for uri-gnome-3-36 in 5 minutes and 12 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #671554
build-arch

00:04:15

passed #671553
build-fedora

00:05:11

passed #671552
build-ubuntu

00:02:10