Fix Python kernel to Python 3

1 job from master in 14 minutes and 3 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #124994558
test_non_release_branches

00:14:03

 
Name Stage Failure
failed
test_non_release_branches Test
7f34616f1000-7f34616f2000 r--p 00023000 08:09 1580375                    /lib/x86_64-linux-gnu/ld-2.24.so
7f34616f2000-7f34616f3000 rw-p 00024000 08:09 1580375 /lib/x86_64-linux-gnu/ld-2.24.so
7f34616f3000-7f34616f4000 rw-p 00000000 00:00 0
7ffef546e000-7ffef548f000 rw-p 00000000 00:00 0 [stack]
7ffef5541000-7ffef5544000 r--p 00000000 00:00 0 [vvar]
7ffef5544000-7ffef5546000 r-xp 00000000 00:00 0 [vdso]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0 [vsyscall]
Aborted (core dumped)
ERROR: Job failed: exit code 1