libkas: Do not sys.exit from a coroutine

That only creates exceptions and complaints if more routines are running
or we are already in the exiting process. Rather leave the coroutine and
catch the error on the waiting end.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

kas/libkas.py

@@ -122,7 +122,6 @@ def run_cmd_async(cmd, cwd, env=None, fail=True, shell=False, liveupdate=True):
         for line in logo.stderr:
             msg += line
         logging.error(msg)
-        sys.exit(ret)
 
     return (ret, ''.join(logo.stdout))
 
@@ -134,8 +133,11 @@ def run_cmd(cmd, cwd, env=None, fail=True, shell=False, liveupdate=True):
     # pylint: disable=too-many-arguments
 
     loop = asyncio.get_event_loop()
-    return loop.run_until_complete(
+    (ret, output) = loop.run_until_complete(
         run_cmd_async(cmd, cwd, env, fail, shell, liveupdate))
+    if ret and fail:
+        sys.exit(ret)
+    return (ret, output)
 
 
 def find_program(paths, name):