/lib/udev/rules.d/85-mouseemu.rules is in mouseemu 0.16-0ubuntu9.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | # Send mouseemu a HUP signal if a new event device is connected
ACTION=="add", KERNEL=="event[0-9]*", RUN+="/bin/sh -c '/bin/kill -HUP $$(pidof mouseemu)'"
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