You can solve it by changing the first line of
/usr/bin/kopete_latexconvert.sh from#!/bin/sh to #!/bin/bash
It seems that the author assumes sh links to bash, and I think it is not
the case for Ubuntu distributions.
** Changed in: kopete (Ubuntu)
Status: Unconfirmed => Confirmed
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Problem with kopetex
https://launchpad.net/bugs/71665