On Line #46 of the bzr plugin there's a mistalke. Instead of:
my @cmdline = ("bzr", $config{srcdir}, "update");
It should be:
my @cmdline = ("bzr", "update", $config{srcdir});
The former produces errors such as "bzr: ERROR: unknown command "/home/user/ikiwiki/posts", "'bzr /home/user/ikiwiki/posts update' failed: Inappropriate ioctl for device at /usr/share/perl5/IkiWiki/Rcs/bzr.pm line 48.".