shade_check does not raise an error but only prints a warning, produces no output file, and exit status 0

[MEschenbacher]

We've noticed that aclgen --shade_check does not raise an error (as described in the README) but only prints a warning, produces no output file, and exits with status 0. We expected the command to fail in such a case i.e. actually produce both, a more grave log message e.g. level error as well as exit status != 0.