[web] get rid of spurious '[Errno 2] No such file or directory' on load This was caused by can_do_pdf_conversion() which tries to use '/usr/bin/fop'. When fop was not available, an OSError was raised by suprocess.Popen. This changeset first checks for /usr/bin/fop presence, then tries to run fop. If an error occurs, log it instead of printing it. NOTE for later: why do we test explicitly for "/usr/bin/fop" rather than simply "fop" ?

/var/log/cubicweb/*.log {
        weekly
        missingok
        rotate 10
        compress
        delaycompress
        notifempty
        create 640 root adm
        sharedscripts
        postrotate
           if [ -x /usr/sbin/invoke-rc.d ]; then \
              invoke-rc.d cubicweb reload > /dev/null; \
           else \
              /etc/init.d/cubicweb reload > /dev/null; \
           fi; \
        endscript
}