DEBUG: Executing timeout(0): /usr/sbin/mock-helper umount /var/lib/mock/fedora-development-i386-postfix/root/proc
Traceback (most recent call last):
  File "/usr/bin/mock", line 1140, in <module>
    main()
  File "/usr/bin/mock", line 1137, in main
    do_rebuild(config_opts, srpms)
  File "/usr/bin/mock", line 997, in do_rebuild
    my.prep()
  File "/usr/bin/mock", line 262, in prep
    self.yum(cmd)
  File "/usr/bin/mock", line 280, in yum
    (retval, output) = self.do(command)
  File "/usr/bin/mock", line 607, in do
    w.write(line)
IOError: [Errno 32] Broken pipe