Comment 3 for bug 342359

I noticed a bunch of loopback files were not removed after several runs:
$ sudo losetup -a
/dev/loop0: [0802]:1712191 (/tmp/vmbuilderoz9Ae3/disk0.img)
/dev/loop1: [0802]:1712192 (/tmp/vmbuilderZ25Vlg/disk0.img)
/dev/loop2: [0802]:1712199 (/tmp/vmbuilderMYw8D9/disk0.img)
/dev/loop3: [0802]:1712202 (/tmp/vmbuildertNVvQu/disk0.img)
/dev/loop4: [0802]:1712205 (/tmp/vmbuilderdfXyav/disk0.img)
/dev/loop5: [0802]:1712208 (/tmp/vmbuilderPyYKWF/disk0.img)

So then I tried to see why:
$ sudo lsof | grep loop[0-5]
lsof: WARNING: can't stat() fuse.gvfs-fuse-daemon file system /home/jamie/.gvfs
      Output information may be incomplete.
loop5 1831 root cwd DIR 8,2 4096 2 /
loop5 1831 root rtd DIR 8,2 4096 2 /
loop5 1831 root txt unknown /proc/1831/exe
loop3 16839 root cwd DIR 8,2 4096 2 /
loop3 16839 root rtd DIR 8,2 4096 2 /
loop3 16839 root txt unknown /proc/16839/exe
loop0 17985 root cwd DIR 8,2 4096 2 /
loop0 17985 root rtd DIR 8,2 4096 2 /
loop0 17985 root txt unknown /proc/17985/exe
loop2 22974 root cwd DIR 8,2 4096 2 /
loop2 22974 root rtd DIR 8,2 4096 2 /
loop2 22974 root txt unknown /proc/22974/exe
loop4 26281 root cwd DIR 8,2 4096 2 /
loop4 26281 root rtd DIR 8,2 4096 2 /
loop4 26281 root txt unknown /proc/26281/exe
loop1 32714 root cwd DIR 8,2 4096 2 /
loop1 32714 root rtd DIR 8,2 4096 2 /
loop1 32714 root txt unknown /proc/32714/exe