Ubuntu: add base repos to Kolla container image earlier

Previously when building Kolla container images for Ubuntu it was common
to get a dependency error during apt package installation, such as:

  The following packages have unmet dependencies:
    libc6-dev : Depends: libc6 (= 2.35-0ubuntu3.1) but 2.35-0ubuntu3.4 is to be installed

This is caused by the packages in the Ubuntu base image being newer than
those in the release train repository snapshot.

This change fixes the issue by switching to the release train
repositories earlier in the build process, before the first apt command
runs.

It's possible that we may also need to pin the Ubuntu base container
image, but that would be another thing to maintain, so let's try without
for now since this approach is necessary and may be sufficient.

etc/kayobe/kolla.yml

@@ -277,14 +277,20 @@ base_centos_repo_overrides_post_yum_rocky_list: "{{ stackhpc_rocky_9_repos + sta
 base_centos_repo_overrides_post_yum_list: "{{ base_centos_repo_overrides_post_yum_centos_list if kolla_base_distro == 'centos' else base_centos_repo_overrides_post_yum_rocky_list }}"
 stackhpc_yum_repos: "{{ stackhpc_centos_stream_repos if kolla_base_distro == 'centos' else stackhpc_rocky_9_repos }}"
 
-# List of repositories for Ubuntu focal.
-stackhpc_ubuntu_focal_repos:
+# List of base repositories for Ubuntu Focal.
+stackhpc_ubuntu_focal_base_repos:
   - "deb {{ stackhpc_repo_ubuntu_focal_url }} focal main universe"
   - "deb {{ stackhpc_repo_ubuntu_focal_url }} focal-updates main universe"
   - "deb {{ stackhpc_repo_ubuntu_focal_url }} focal-backports main universe"
   - "deb {{ stackhpc_repo_ubuntu_focal_security_url }} focal-security main universe"
+
+# List of UCA repositories for Ubuntu Focal.
+stackhpc_ubuntu_focal_uca_repos:
   - "deb {{ stackhpc_repo_ubuntu_cloud_archive_url }} focal-updates/{{ openstack_release }} main"
 
+# List of repositories for Ubuntu Focal.
+stackhpc_ubuntu_focal_repos: "{{ stackhpc_ubuntu_focal_base_repos + stackhpc_ubuntu_focal_uca_repos }}"
+
 # Whether to revert to the upstream mirrors in built Kolla container images.
 stackhpc_kolla_clean_up_repo_mirrors: true
 
@@ -304,6 +310,13 @@ kolla_build_blocks:
                -e '/\[{{ repo.tag }}\]/,/^\[/ s|^\(name.*\)|\1\nbaseurl={{ repo.url }}|' /etc/yum.repos.d/{{ repo.file }}{% if not loop.last %} && \
     {% endif %}
     {% endfor %}
+    {% else %}
+    RUN \
+        rm /etc/apt/sources.list && \
+    {% for repo in stackhpc_ubuntu_focal_base_repos %}
+        echo '{{ repo }}' >> /etc/apt/sources.list {% if not loop.last %} && \
+    {% endif %}
+    {% endfor %}
     {% endif %}
   base_centos_repo_overrides_post_yum: |
     {# fixme #}
@@ -320,9 +333,13 @@ kolla_build_blocks:
                -e '/\[{{ repo.tag }}\]/,/^\[/ s|^\(name.*\)|\1\nbaseurl={{ repo.url }}|' /etc/yum.repos.d/{{ repo.file }}{% if not loop.last %} &&{% endif %} \
     {% endfor %}
     {% endif %}
+  # With the UCA keyring installed we can now add all repos.
   base_ubuntu_package_sources_list: |
+    {% if stackhpc_kolla_clean_up_repo_mirrors | bool %}
+    COPY sources.list.ubuntu /etc/apt/sources.list.backup
+    {% endif %}
     RUN \
-        mv /etc/apt/sources.list /etc/apt/sources.list.backup && \
+        rm /etc/apt/sources.list && \
     {% for repo in stackhpc_ubuntu_focal_repos %}
         echo '{{ repo }}' >> /etc/apt/sources.list {% if not loop.last %} && \
     {% endif %}

releasenotes/notes/ubuntu-image-early-repos-08b4da6165f5fa11.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes an issue with Kolla container image builds for Ubuntu where the
+    release train package repositories could be behind the container image,
+    leading to image build failures.