/usr/share/unity8-desktop-session/sensors.txt is in unity8-desktop-session-mir 1.0.10+14.04.20140417.1-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | create proximity
create accel 0.5 1000 0.1
create light 0 10 0.5
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