devtool: use DevtoolError for error handling

Use DevtoolError exception more widely for handling error cases. This
exception is now caught in the main script and raising it can be used to
exit with an error. This hopefully simplifies error handling. The
change also makes exit codes more consistent, always returning '1' when
an error occurs.

(From OE-Core rev: 2e4f1dcade7ccb581c7a390c32163ea3deeac6d5)

Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/devtool/__init__.py

@@ -25,6 +25,12 @@ import logging
 
 logger = logging.getLogger('devtool')
 
+
+class DevtoolError(Exception):
+    """Exception for handling devtool errors"""
+    pass
+
+
 def exec_build_env_command(init_path, builddir, cmd, watch=False, **options):
     """Run a program in bitbake build context"""
     import bb