Comment 15 for bug 1730627

verification that it fixes the problem for me, re: autopkgtest. As that was the same cause/problem as initial reporter's, I expect it should be fixed for them as well.

ddstreet@thorin:~/bugs/lp1730627/verification$ pull-lp-source lsb-base trusty
pull-lp-source: Using source package 'lsb' for binary package 'lsb-base'
pull-lp-source: Found lsb 4.1+Debian11ubuntu6.2 in trusty
pull-lp-source: Good signature by Steve Langasek <email address hidden> (0x568D30F321B2133D)
pull-lp-source: Downloading lsb_4.1+Debian11ubuntu6.2.tar.xz from archive.ubuntu.com (0.063 MiB)
dpkg-source: info: extracting lsb in lsb-4.1+Debian11ubuntu6.2
dpkg-source: info: unpacking lsb_4.1+Debian11ubuntu6.2.tar.xz
ddstreet@thorin:~/bugs/lp1730627/verification$ autopkgtest -U lsb_4.1+Debian11ubuntu6.2.dsc -- lxd ubuntu-daily:trusty
autopkgtest [14:16:23]: version 5.1
autopkgtest [14:16:23]: host thorin.lan; command line: /usr/bin/autopkgtest -U lsb_4.1+Debian11ubuntu6.2.dsc -- lxd ubuntu-daily:trusty
...
(normal setup output)
...
autopkgtest [14:17:36]: testbed dpkg architecture: amd64
autopkgtest [14:17:38]: testbed running kernel: Linux 4.15.0-10-generic #11-Ubuntu SMP Tue Feb 13 18:23:35 UTC 2018
autopkgtest [14:17:38]: @@@@@@@@@@@@@@@@@@@@ source lsb_4.1+Debian11ubuntu6.2.dsc
autopkgtest [14:17:42]: ERROR: "dpkg --unpack /tmp/autopkgtest.Mrh8tN/autopkgtest-satdep.deb" failed with stderr "dpkg-deb: error: archive '/tmp/autopkgtest.Mrh8tN/autopkgtest-satdep.deb' has premature member 'control.tar.xz' before 'control.tar.gz', giving up
dpkg: error processing archive /tmp/autopkgtest.Mrh8tN/autopkgtest-satdep.deb (--unpack):
 subprocess dpkg-deb --control returned error exit status 2
Errors were encountered while processing:
 /tmp/autopkgtest.Mrh8tN/autopkgtest-satdep.deb

using -proposed package:

ddstreet@thorin:~/bugs/lp1730627/verification$ autopkgtest --apt-pocket proposed=dpkg -U lsb_4.1+Debian11ubuntu6.2.dsc -- lxd ubuntu-daily:trusty
autopkgtest [14:19:13]: version 5.1
autopkgtest [14:19:13]: host thorin.lan; command line: /usr/bin/autopkgtest --apt-pocket proposed=dpkg -U lsb_4.1+Debian11ubuntu6.2.dsc -- lxd ubuntu-daily:trusty
...
(normal setup output)
...
Preparing to unpack .../dpkg-dev_1.17.5ubuntu5.8_all.deb ...
Unpacking dpkg-dev (1.17.5ubuntu5.8) ...
...
dpkg-buildpackage: binary only upload (no source included)
dpkg-source: info: using options from src/debian/source/options: --compression=xz
* SKIP no tests in this package
autopkgtest [14:24:14]: @@@@@@@@@@@@@@@@@@@@ summary
* SKIP no tests in this package

autopkgtest is able to continue with -proposed dpkg.