fix(cli): Print statement in global error handler

This is the last place we could be writing to stderr from our code. It
seems unlikely this is the root cause of the devstack issue, since our
monkey-patch test should have turned this up, but let's remove it to
be absolutely certain.

Change-Id: Id454d9affcf060d5308f965e25119693ec790624
Partial-Bug: #1287490

marconi/common/cli.py

@@ -32,7 +32,6 @@ def _fail(returncode, ex):
     :param ex: the error that occurred
     """
 
-    print(ex, file=sys.stderr)
     LOG.exception(ex)
     sys.exit(returncode)