Piuparts fails when attempting to mount ‘proc’

[Ben Finney <bignose@debian.org>]

Howdy all,

What is causing Piuparts to try mounting a file that doesn't exist,
during an SBuild session?

The ‘sbuild --dist unstable foo_1.2.3-1.dsc’ fails in the Piuparts
step::

=====
[…]
0m0.0s DEBUG: Created temporary directory /tmp/tmpF4WJfq
0m0.0s DEBUG: Copying /srv/chroot/unstable-amd64-sbuild/ into /tmp/tmpF4WJfq
0m0.0s DEBUG: Starting command: ['mount', '-t', 'proc', 'proc', '/tmp/tmpF4WJfq/proc']
0m0.0s DEBUG: Command ok: ['mount', '-t', 'proc', 'proc', '/tmp/tmpF4WJfq/proc']
Traceback (most recent call last):
  File "/usr/sbin/piuparts", line 3360, in <module>
    main()
  File "/usr/sbin/piuparts", line 3345, in main
    process_packages(package_list)
  File "/usr/sbin/piuparts", line 3246, in process_packages
    chroot.create()
  File "/usr/sbin/piuparts", line 781, in create
    self.mount_proc()
  File "/usr/sbin/piuparts", line 1652, in mount_proc
    os.symlink("../proc/mounts", etcmtab)
OSError: [Errno 2] No such file or directory

E: Piuparts run failed.
=====

I can't find where that ‘mount’ command is defined, so I don't think it
is a bad configuration. That could be wrong though.

-- 
 \     “I went camping and borrowed a circus tent by mistake. I didn't |
  `\      notice until I got it set up. People complained because they |
_o__)                           couldn't see the lake.” —Steven Wright |
Ben Finney