collision error reported with new d-i xenial hwe kernels

Build process saw this error today:

Building images for v2 streams
+ PATH=/build/config/maas/bin:/build/local/scripts:/build/local/scripts:/build/local/scripts:/build/local/scripts:/build/local/scripts:/build/local/scripts:/build/local/scripts:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin
+ meph2-build --image-format root-tar -vv --enable-di i386 xenial 20170216 livecd.ubuntu-cpc.rootfs.tar.xz binary/maas/
mining d-i data from 2 places in 2 threads. [['xenial'] * ['updates', 'release'] * ['i386']].
0 mining xenial from http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386
1 mining xenial from http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-i386
downloading http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.6/images/SHA256SUMS
downloading http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-i386/20101020ubuntu448/images/SHA256SUMS
downloading gpg http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.6/images/SHA256SUMS.gpg
downloading gpg http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-i386/20101020ubuntu448/images/SHA256SUMS.gpg
downloading http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.6/images/MD5SUMS
downloading http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-i386/20101020ubuntu448/images/MD5SUMS
downloading http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-i386/20101020ubuntu450/images/SHA256SUMS
downloading http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.9/images/SHA256SUMS
downloading gpg http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-i386/20101020ubuntu450/images/SHA256SUMS.gpg
downloading gpg http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.9/images/SHA256SUMS.gpg
downloading http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-i386/20101020ubuntu450/images/MD5SUMS
downloading http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.9/images/MD5SUMS
downloading http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.10/images/SHA256SUMS
downloading http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-i386/20101020ubuntu451/images/SHA256SUMS
downloading gpg http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.10/images/SHA256SUMS.gpg
downloading gpg http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-i386/20101020ubuntu451/images/SHA256SUMS.gpg
downloading http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.10/images/MD5SUMS
downloading http://archive.ubuntu.com/ubuntu/dists/xenial/main/installer-i386/20101020ubuntu451/images/MD5SUMS
0 mining xenial at http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386 failed
Traceback (most recent call last):
  File "/build/config/maas/meph2/netinst.py", line 497, in run
    found = mine_md(url=data['inst_url'], release=release)
  File "/build/config/maas/meph2/netinst.py", line 468, in mine_md
    separators=(',', ': '))))
Exception: Name Collision: xexegeninnet.default[xenial]: {
 "basename": "initrd.gz",
 "ftype": "initrd",
 "image-format": "default",
 "initrd-flavor": "netboot",
 "kernel-flavor": "generic",
 "kernel-release": "xenial",
 "md5": "a4bd825248371c5daa4fb8d6480a7667",
 "pubdate": "Wed, 15 Feb 2017 14:04:00 +0000",
 "sha256": "bc69b5dae20124a31092f99a8cb7b8da4b7b29f59ce09db0674ac2761c1336d7",
 "size": 38938040,
 "url": "http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.10/images/hwe-netboot/ubuntu-installer/i386/initrd.gz"
}.
Collided with: {
 "basename": "initrd.gz",
 "ftype": "initrd",
 "image-format": "default",
 "initrd-flavor": "netboot",
 "kernel-flavor": "generic",
 "kernel-release": "xenial",
 "md5": "7674fef6d2adb56c73ea1458c07aebe3",
 "pubdate": "Wed, 15 Feb 2017 14:04:00 +0000",
 "sha256": "bae586538c8c6d55d38b84fa0cd7842598917a9ec7eeb7d437583da82d4b7480",
 "size": 38755418,
 "url": "http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.10/images/netboot/ubuntu-installer/i386/initrd.gz"
}
finished mining of ['xenial'] * ['updates', 'release'] * ['i386']. now processing.
There were 1 errors, raising first
Traceback (most recent call last):
  File "/build/config/maas/bin/meph2-build", line 25, in <module>
    call_entry_point("meph2.commands.build_image.main")
  File "/build/config/maas/bin/meph2-build", line 22, in call_entry_point
    sys.exit(getattr(sys.modules[istr], ent)())
  File "/build/config/maas/meph2/commands/build_image.py", line 102, in main
    verbosity=vlevel, img_format=args.image_format)
  File "/build/config/maas/meph2/stream.py", line 145, in create_version
    releases=[release], arches=[arch], pockets=di_pockets)
  File "/build/config/maas/meph2/netinst.py", line 649, in get_di_kernelinfo
    pockets=pockets)
  File "/build/config/maas/meph2/netinst.py", line 156, in __init__
    self._get_products(path=None)
  File "/build/config/maas/meph2/netinst.py", line 177, in _get_products
    pockets=self.pockets)
  File "/build/config/maas/meph2/netinst.py", line 638, in get_products_data
    raise errors[0]
  File "/build/config/maas/meph2/netinst.py", line 497, in run
    found = mine_md(url=data['inst_url'], release=release)
  File "/build/config/maas/meph2/netinst.py", line 468, in mine_md
    separators=(',', ': '))))
Exception: Name Collision: xexegeninnet.default[xenial]: {
 "basename": "initrd.gz",
 "ftype": "initrd",
 "image-format": "default",
 "initrd-flavor": "netboot",
 "kernel-flavor": "generic",
 "kernel-release": "xenial",
 "md5": "a4bd825248371c5daa4fb8d6480a7667",
 "pubdate": "Wed, 15 Feb 2017 14:04:00 +0000",
 "sha256": "bc69b5dae20124a31092f99a8cb7b8da4b7b29f59ce09db0674ac2761c1336d7",
 "size": 38938040,
 "url": "http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.10/images/hwe-netboot/ubuntu-installer/i386/initrd.gz"
}.
Collided with: {
 "basename": "initrd.gz",
 "ftype": "initrd",
 "image-format": "default",
 "initrd-flavor": "netboot",
 "kernel-flavor": "generic",
 "kernel-release": "xenial",
 "md5": "7674fef6d2adb56c73ea1458c07aebe3",
 "pubdate": "Wed, 15 Feb 2017 14:04:00 +0000",
 "sha256": "bae586538c8c6d55d38b84fa0cd7842598917a9ec7eeb7d437583da82d4b7480",
 "size": 38755418,
 "url": "http://archive.ubuntu.com/ubuntu/dists/xenial-updates/main/installer-i386/20101020ubuntu451.10/images/netboot/ubuntu-installer/i386/initrd.gz"
}