Running AREX as ordinary user - INTERNAL plugin nice problem - permission denied

When running arex as ordinary user and submitting a job through the internal interface

arcsub -d  5 -c localhost --direct -S org.nordugrid.internal hello.xrls

I see nice: .... Permission denied in the std.err of the job

[centos@atlas-offline-tests arc-testing]$ cat /arc/session/DE9KDmhYiFtnbZK2tmAJvREmgBOcFnABFKDm5LMKDmABFKDmO3HQEn/std.err 
nice: /home/centos/arc-testing/runhello.sh: Permission denied

This is my setup:

[centos@atlas-offline-tests arc-testing]$ cat hello.xrls
&(executable=/home/centos/arc-testing/runhello.sh)
(jobname=hello_autodeploy)
(stdout=std.out)
(stderr=std.err)
(cpuTime="1 hours")
(memory="1000")
(inputfiles=("file.txt" "/home/centos/arc-testing/file.txt"))
(outputfiles=("output.txt" "" ))

[centos@atlas-offline-tests arc-testing]$ cat runhello.sh
#!/bin/sh
echo "Computing md5sum for file.txt";md5sum file.txt>>output.txt;
echo "Am sleeping for 30 seconds"
sleep 30

I have set:

export PATH=/grid/software/bin:/grid/software/sbin:$PATH
export LD_LIBRARY_PATH=/grid/software/lib/arc
export PYTHONPATH=/grid/software/lib64/python2.7/site-packages:/grid/software/lib64/python2.7/site-packages/arc:$PYTHONPATH

export ARC_LOCATION=/grid/software
export ARC_CONFIG=/grid/software/etc/arc.conf

My arc.conf:

[common]
loglevel=5

[lrms]
lrms=fork

[arex]
pidfile=/arc/arex.pid
controldir=/arc/control
sessiondir=/arc/session
logfile=/arc/arc-logs/arex.log


[infosys]
loglevel=2
logfile=/arc/arc-logs/infoprovider.log


[queue:main]
[infosys/cluster]