Comment 5 for bug 1737637

Verified 1.1ubuntu1.18.04.7~16.04.2 in Xenial:

root@x-uu-verify:~# apt update -qq
21 packages can be upgraded. Run 'apt list --upgradable' to see them.
root@x-uu-verify:~# apt install git=1:2.7.4-0ubuntu1
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following package was automatically installed and is no longer required:
  libfreetype6
Use 'apt autoremove' to remove it.
Suggested packages:
  git-daemon-run | git-daemon-sysvinit git-doc git-el git-email git-gui gitk gitweb git-arch git-cvs git-mediawiki git-svn
The following packages will be DOWNGRADED:
  git
0 upgraded, 0 newly installed, 1 downgraded, 0 to remove and 21 not upgraded.
Need to get 3,006 kB of archives.
After this operation, 73.7 kB disk space will be freed.
Do you want to continue? [Y/n]
Get:1 http://archive.ubuntu.com/ubuntu xenial/main amd64 git amd64 1:2.7.4-0ubuntu1 [3,006 kB]
Fetched 3,006 kB in 0s (13.0 MB/s)
dpkg: warning: downgrading git from 1:2.7.4-0ubuntu1.6 to 1:2.7.4-0ubuntu1
(Reading database ... 25724 files and directories currently installed.)
Preparing to unpack .../git_1%3a2.7.4-0ubuntu1_amd64.deb ...
Unpacking git (1:2.7.4-0ubuntu1) over (1:2.7.4-0ubuntu1.6) ...
Setting up git (1:2.7.4-0ubuntu1) ...
root@x-uu-verify:~# mv /etc/bash_completion.d/git-prompt /etc/bash_completion.d/git-prompt.bak
root@x-uu-verify:~# mkdir /etc/bash_completion.d/git-prompt
root@x-uu-verify:~# unattended-upgrade --verbose --dry-run
Initial blacklisted packages:
Initial whitelisted packages:
Starting unattended upgrades script
Allowed origins are: ['o=Ubuntu,a=xenial', 'o=Ubuntu,a=xenial-security', 'o=UbuntuESM,a=xenial']
Traceback (most recent call last):
  File "/usr/bin/unattended-upgrade", line 1485, in <module>
    main(options)
  File "/usr/bin/unattended-upgrade", line 1275, in main
    if conffile_prompt(item.destfile):
  File "/usr/bin/unattended-upgrade", line 671, in conffile_prompt
    with open(prefix + conf_file, 'rb') as fb:
IsADirectoryError: [Errno 21] Is a directory: '/etc/bash_completion.d/git-prompt'
root@x-uu-verify:~# vi /etc/apt/sources.list
root@x-uu-verify:~# apt update -qq
30 packages can be upgraded. Run 'apt list --upgradable' to see them.
root@x-uu-verify:~# apt install -y -qq unattended-upgrades
The following package was automatically installed and is no longer required:
  libfreetype6
Use 'apt autoremove' to remove it.
Suggested packages:
  bsd-mailx default-mta | mail-transport-agent needrestart
The following packages will be upgraded:
  unattended-upgrades
1 upgraded, 0 newly installed, 0 to remove and 29 not upgraded.
Need to get 40.1 kB of archives.
After this operation, 69.6 kB of additional disk space will be used.
Preconfiguring packages ...
(Reading database ... 25723 files and directories currently installed.)
Preparing to unpack .../unattended-upgrades_1.1ubuntu1.18.04.7~16.04.2_all.deb ...
Unpacking unattended-upgrades (1.1ubuntu1.18.04.7~16.04.2) over (0.90ubuntu0.10) ...
Processing triggers for man-db (2.7.5-1) ...
Processing triggers for systemd (229-4ubuntu21.17) ...
Processing triggers for ureadahead (0.100.0-19) ...
Setting up unattended-upgrades (1.1ubuntu1.18.04.7~16.04.2) ...
Installing new version of config file /etc/kernel/postinst.d/unattended-upgrades ...
Installing new version of config file /etc/pm/sleep.d/10_unattended-upgrades-hibernate ...
root@x-uu-verify:~# unattended-upgrade --verbose --dry-run
Initial blacklisted packages:
Initial whitelisted packages:
Starting unattended upgrades script
Allowed origins are: o=Ubuntu,a=xenial, o=Ubuntu,a=xenial-security, o=UbuntuESM,a=xenial
Option --dry-run given, *not* performing real actions
Packages that will be upgraded: busybox-initramfs busybox-static git libpolkit-agent-1-0 libpolkit-backend-1-0 libpolkit-gobject-1-0 ntfs-3g policykit-1 snapd ubuntu-core-launcher
Writing dpkg log to /var/log/unattended-upgrades/unattended-upgrades-dpkg.log
/usr/bin/dpkg --status-fd 9 --unpack --auto-deconfigure /var/cache/apt/archives/git_1%3a2.7.4-0ubuntu1.6_amd64.deb
/usr/bin/dpkg --status-fd 11 --configure git:amd64
/usr/bin/dpkg --status-fd 13 --configure --pending
/usr/bin/dpkg --status-fd 9 --unpack --auto-deconfigure /var/cache/apt/archives/libpolkit-backend-1-0_0.105-14.1ubuntu0.5_amd64.deb
/usr/bin/dpkg --status-fd 11 --configure libpolkit-backend-1-0:amd64
/usr/bin/dpkg --status-fd 13 --configure --pending
/usr/bin/dpkg --status-fd 9 --unpack --auto-deconfigure /var/cache/apt/archives/busybox-initramfs_1%3a1.22.0-15ubuntu1.4_amd64.deb
/usr/bin/dpkg --status-fd 11 --configure busybox-initramfs:amd64
/usr/bin/dpkg --status-fd 13 --configure --pending
/usr/bin/dpkg --status-fd 9 --unpack --auto-deconfigure /var/cache/apt/archives/libpolkit-agent-1-0_0.105-14.1ubuntu0.5_amd64.deb
/usr/bin/dpkg --status-fd 11 --configure libpolkit-agent-1-0:amd64
/usr/bin/dpkg --status-fd 13 --configure --pending
/usr/bin/dpkg --status-fd 9 --unpack --auto-deconfigure /var/cache/apt/archives/ntfs-3g_1%3a2015.3.14AR.1-1ubuntu0.2_amd64.deb
/usr/bin/dpkg --status-fd 11 --configure ntfs-3g:amd64
/usr/bin/dpkg --status-fd 13 --configure --pending
/usr/bin/dpkg --status-fd 9 --unpack --auto-deconfigure /var/cache/apt/archives/busybox-static_1%3a1.22.0-15ubuntu1.4_amd64.deb
/usr/bin/dpkg --status-fd 11 --configure busybox-static:amd64
/usr/bin/dpkg --status-fd 13 --configure --pending
/usr/bin/dpkg --status-fd 9 --unpack --auto-deconfigure /var/cache/apt/archives/libpolkit-gobject-1-0_0.105-14.1ubuntu0.5_amd64.deb
/usr/bin/dpkg --status-fd 11 --configure libpolkit-gobject-1-0:amd64
/usr/bin/dpkg --status-fd 13 --configure --pending
/usr/bin/dpkg --status-fd 9 --unpack --auto-deconfigure /var/cache/apt/archives/policykit-1_0.105-14.1ubuntu0.5_amd64.deb
/usr/bin/dpkg --status-fd 11 --configure policykit-1:amd64
/usr/bin/dpkg --status-fd 13 --configure --pending
/usr/bin/dpkg --status-fd 9 --unpack --auto-deconfigure /var/cache/apt/archives/ubuntu-core-launcher_2.37.4ubuntu0.1_amd64.deb /var/cache/apt/archives/snapd_2.37.4ubuntu0.1_amd64.deb
/usr/bin/dpkg --status-fd 11 --configure snapd:amd64 ubuntu-core-launcher:amd64
/usr/bin/dpkg --status-fd 13 --configure --pending
All upgrades installed
root@x-uu-verify:~#