Fix wrong python build-dependency.

8 jobs for debian in 6 minutes and 39 seconds (queued for 2 seconds)
latest
Status Job ID Name Coverage
  Build
passed #326904
build

00:03:02

 
  Test
passed #326909
autopkgtest

00:03:35

passed #326910
blhc

00:01:21

passed #326908
lintian

00:01:30

passed #326911
piuparts

00:03:25

passed #326907
reprotest

00:02:42

passed #326906
test-build-all

00:03:10

passed #326905
test-build-any

00:02:03