convert fail silently if cvsps is not installed

[Patrick Mézard]

marco gaddoni a écrit :
> 
> yes you are right.
> see the updated patch.
> i have copied (adding a bug) that function from
> run-tests.py.
> shall i update that function too?

* Would util.find_exe() be enough to do this ?
* The cvs converter also requires cvs client.
* The abort message could be changed from "foobar executable not found. cant convert" to "required foobar executable not found".

Except for these, this patch is definitely a good idea.

--
Patrick Mézard