A fatal from update all content does not provide loggable errormessages

After some small changes to the doctypes, I did update all content. This failed. The cause was not explained in the log4j logs. When I ran it locally from Jetty, the cause was explained on the console where I started Jetty. Frank and Bart told me that it was NOT possible to configure log4j such that these explanations would go in the logs. This is because the logging is not coded, only writing to the console.

Use case 1:
When I run locally and I want to keep messages for future reference or a bug report, messages printed on my console but not in the logs, I use my mouse-buffer to cut and paste into a file. Sometimes the message are so long they do not fit in my mouse buffer. So in that case it is a lot of handwork to get all the messages in a bug report.
This problem would not occur if all error messages could be configured to go the log files.
The missing error messages were about ambiguous field names, which occurred after upgrading. In older versions, inherited fields had to be supplied in the doctypes. In newer versions it is forbidden to supply them. No warning are given about this untill an 'update all content'.

Use case 2:
On the server I performed `update all content'. It failed. I received the logs from Bart, but they do not give information about it. Even catalina.out does not contain any information about it.