LXDE-pi/lxpanel keeps an internal log file

[aakoskin]

LXDE-pi/lxpanel keeps an internal log file at $HOME/.cache/lxsession/LXDE-pi/run.log, and e.g. on RPi3 with official touchscreen the following log spam appears every time switching between windows:

** (lxpanel:1194): WARNING **: 17:41:28.635: lxpanel : X error: BadMatch (invalid parameter attributes)

The log file does not seem to be managed/size limited at all, and also it results in periodic disk writes, and user cannot control the logging at all.

Errors should be logged at journal only for better visibility and control. If the run.log is meant for debugging then it should be disabled by default.