"Error found when loading /etc/profile"

Same thing happened to my when upgrading Mate to 17.10.

I went to System -> Preferences -> Look and Feel -> Language Support.

I'd previously selected English (UK) as my menu/windows language so on first opening this up I was prompted to upgrade, which I did.

My intention, and what I went on to do, was to change the "keyboard input method system" from "XIM" to "None". Rebooted, and that seemed to clear the error message at login without any other ill effects - so far!

My logic... I don't have ibus on my machine and I didn't see the need for it if I don't need exotic fonts. My default display manager is lightdm, so that would trip the first condition in the 21_ibus.rc file, taking me to line 6, which seems to disable the IBUS_SYNC mode and force XIM. Again, not installing ibus, so can't use the ibus-deamon, therefore I can't have the XIM option - so I switched the keyboard option, as indicated above, and that seemed to work.

To do that on KDE open a terminal and type

 im-config -n none

Suspect it's a minor configuration issue, but would welcome learning if there's a more robust solution.

I had the same issue after upgrade to 17.10. Temporary work around by set the keyboard input method system to none in language support.