"sudo apt purge kodi" sorted it out. No errors on next session login.
This can be closed, but I'm not sure I have the rights.
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package kodi-data 15.2+dfsg1-3ubuntu1 failed to install/upgrade:
trying to overwrite '/usr/share/xsessions/kodi.desktop', which is also
in package kodi 2:16.1~git20160424.1410-final-0wily
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