dib fails when using custom apt-sources

[Oded Le'Sage]

When trying to use an internal/custom debian package repo by using apt-sources element, DIB fails if a package is installed right after the repo key is added.

disk-image-create --version
2.14.2

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To reproduce (assumes tripleo-image-elements has been cloned in the same root dir as DIB):
.
|-- diskimage-builder
`-- tripleo-image-elements

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export DIB_APT_SOURCES=/etc/apt/sources.list
export DIB_ADD_APT_KEYS=/etc/apt/trusted.gpg.d
export ELEMENTS_PATH=tripleo-image-elements/elements

disk-image-create ubuntu vm apt-sources os-collect-config

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Relevant log entries
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2018-05-01 20:58:33.347 | dib-run-parts Running /tmp/in_target.d/pre-install.d/02-add-apt-keys
2018-05-01 20:58:33.442 | OK
2018-05-01 20:58:33.443 | dib-run-parts 02-add-apt-keys completed
2018-05-01 20:58:33.443 | dib-run-parts Running /tmp/in_target.d/pre-install.d/02-package-installs
2018-05-01 20:58:33.561 | Map install for svc-map: PyYAML
2018-05-01 20:58:33.561 | Map install for epel: wget, yum-utils
2018-05-01 20:58:33.561 | Running command: ['install-packages', 'python-yaml']
2018-05-01 20:58:33.561 | > Reading package lists...
2018-05-01 20:58:33.561 | > Building dependency tree...
2018-05-01 20:58:33.561 | > Reading state information...
2018-05-01 20:58:33.562 | > E: Unable to locate package python-yaml
2018-05-01 20:58:33.562 | returncode: 100
2018-05-01 20:58:33.562 | install-packages failed with returncode 100
2018-05-01 20:58:33.804 | INFO diskimage_builder.block_device.blockdevice [-] State already cleaned - no way to do anything here

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Summary
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os-collect config tries to install the deb package for PyYAML, but since an apt-get update hasn't been performed after adding the apt key, it cannot locate the package. While I came across this with os-collect-config it could be any package. The dpkg element doesn't apt update until 99-apt-get-update

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/565599

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/565599
Committed: https://git.openstack.org/cgit/openstack/diskimage-builder/commit/?id=10b2a5a4ee1c5c6c16f61277b7795500f0a72886
Submitter: Zuul
Branch: master

commit 10b2a5a4ee1c5c6c16f61277b7795500f0a72886
Author: Oded Le'Sage <email address hidden>
Date: Tue May 1 16:39:01 2018 -0500

    Fixes add-apt-keys in dpkg element

    This commit addresses the issue described in bug 1768354 when using the
    apt-sources element and adding a key to a custom repo, subsequent deb
    package installs fail due no update of the repo before package install

    Change-Id: I968b3422fab2fb2305426d49215391d8ba7499df
    Closes-Bug: 1768354