Hi. I have a test, where I’m expecting keyword’s fail, which causes another keyword’s fail and I would like to catch a full (long) error message generated by the first one. But I met an limitation of maximum number of error lines visible.
Please see the following issue: https://code.google.com/archive/p/robotframework/issues/340
As far as I know it is impossible to change maximum error lines during execution from CLI.
The only way is to change it directly in the Robot Framework source code, http://robot-framework.readthedocs.org/en/2.9.1/_modules/robot/utils/text.html, and setting _MAX_ERROR_LINES variable.

My temporary workaround is to use sed in cron (it is executed very often to avoid situation, when after some updates we have MAX_ERROR_LINES set back to 40):

sudo sed -i 's/_MAX_ERROR_LINES = 40/_MAX_ERROR_LINES = 999/g' /usr/local/lib/python2.7/dist-packages/robot/utils/text.py