pbulk on OS X fails on first package with permission denied

["J. Lewis Muir" <jlmuir%imca-cat.org@localhost>]

Hello, All.

I'm trying to set up a bulk build of pkgsrc-2014Q4 on OS X Yosemite
using pbulk, but the build fails on the very first package with lots and
lots of errors like the following:

--- configure.log ---
===> Installing dependencies for digest-20121220
===> Overriding tools for digest-20121220
/home/pbulk/build/pkgtools/digest/work/.tools/bin/true: line 3: /opt/pkgsrc-world/bulklog/digest-20121220/work.log: Permission denied
/home/pbulk/build/pkgtools/digest/work/.tools/bin/true: line 4: /opt/pkgsrc-world/bulklog/digest-20121220/work.log: Permission denied
[snip: same line 3 and line 4 error messages repeat four times]
===> Extracting for digest-20121220
[snip: same line 3 and line 4 error messages repeat many times]
===> Patching for digest-20121220
[snip: same line 3 and line 4 error messages repeat many times]
===> Creating toolchain wrappers for digest-20121220
[snip: same line 3 and line 4 error messages repeat many times]
[... and so on ...]
---------------------

Looking at the file mentioned,

  /opt/pkgsrc-world/bulklog/digest-20121220/work.log

, I see that it's owned by user "root" and group "wheel" with the
following permissions: -rw-r--r--.  Actually, all the files in
digest-20121220 are that way.  Is this the problem?  The pbulk software
runs the build as the pbulk user, right?  So is the pbulk user trying
to write to work.log but can't because of that file's ownership and
permissions?

I start the bulk build like this:

$ sudo bulkbuild

That will run bulkbuild as root.

I'm following Jonathan Perkin's excellent July 2013 blog post titled,
"Distributed chrooted pkgsrc bulk builds":

  http://www.perkin.org.uk/posts/distributed-chrooted-pkgsrc-bulk-builds.html

Note that this involves applying the following patch to pbulk:

  http://www.netbsd.org/~jperkin/pbulk-joyent.diff

Instead of "/content", I'm using "/opt/pkgsrc-world".  Instead of
"/usr/pkg", I'm using "/opt/pkg".  And instead of "/usr/pbulk", I'm
using "/opt/pbulk".

I'm running on a single host performing concurrent builds
inside chroots, just like the blog post (i.e. pbulk variables
master_ip=127.0.0.1, scan_clients="", and build_clients="").

To test the setup, I have configured pbulk's limited_list variable to
point to a file containing one line:

  security/keychain

Does anyone know what's wrong?  Is there a good way to debug this?  For
example, is there a way to run by hand what pbulk would do so I can
examine the problem interactively?

Thank you!

Lewis