Test plan:
1. Introduce a typo in swagger.json or another spec json file.
2. Restart plack if used or try to access the REST APIs
3. Without the patch, verify that an incomplete error message and potentially lots of stack trace are logged.
4. With the patch, verify that much more meaningful error messages are logged and stack trace is omitted.
5. Fix the problem introduced in step 1 and verify that no messages are logged, or only warning about bundle is logged with Debian Stretch.
6. Repeat with a REST API plugin.
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io> Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>