warn, rather than failing, if kyua is not present

(cherry picked from commit 6cfb2249)
19 jobs for 4-warn-not-fail-v9_12 in 9 minutes and 11 seconds (queued for 11 seconds)
Status Job ID Name Coverage
  Precheck
passed precheck:debian:sid:amd64 #97820
linux docker amd64

00:00:28

failed precheck:debian:sid:amd64 #97754
amd64 docker linux

00:01:18

 
  Build
passed build:centos:centos6:amd64 #97755
amd64 docker linux

00:02:39

passed build:centos:centos7:amd64 #97756
amd64 docker linux

00:02:57

passed build:debian:sid:amd64 #97757
amd64 docker linux

00:01:35

passed build:debian:sid:i386 #97758
i386 docker linux

00:01:32

passed noassert:build:debian:sid:amd64 #97759
amd64 docker linux

00:02:00

 
  Test
passed docs:debian:sid:amd64 #97760
amd64 docker linux

00:00:52

passed install:debian:sid:amd64 #97769
amd64 docker linux

00:03:20

passed noassert:systemtest:debian:sid:amd64 #97771
amd64 docker linux

00:04:59

passed noassert:unittest:debian:sid:amd64 #97770
amd64 docker linux

00:00:48

passed systemtest:centos:centos6:amd64 #97765
amd64 docker linux

00:05:14

passed systemtest:centos:centos7:amd64 #97766
amd64 docker linux

00:04:51

passed systemtest:debian:sid:amd64 #97767
amd64 docker linux

00:04:54

passed systemtest:debian:sid:i386 #97768
i386 docker linux

00:05:27

passed unittest:centos:centos6:amd64 #97761
amd64 docker linux

00:00:57

passed unittest:centos:centos7:amd64 #97762
amd64 docker linux

00:00:57

passed unittest:debian:sid:amd64 #97763
amd64 docker linux

00:00:57

passed unittest:debian:sid:i386 #97764
i386 docker linux

00:00:56