Clarify stdin input

Resolve #836.
3 jobs for clarify-stdin-input in 1 minute and 1 second (queued for 4 seconds)
Status Job ID Name Coverage
  Test
passed #5714
pycodestyle

00:00:18

passed #5715
shellcheck

00:00:20

failed #5713
unit_tests

00:00:21

 
Name Stage Failure
failed
unit_tests Test
  File "/builds/ungleich-public/cdist/cdist/inventory.py", line 358, in __init__
raise cdist.Error("Tag(s) missing")
cdist.Error: Tag(s) missing

----------------------------------------------------------------------
Ran 225 tests in 8.262s

FAILED (errors=1, expected failures=2)
ERROR: Job failed: exit code 1