ci: retry centos vault repo failures using new package_retry yum/dnf plugin

.github/workflows/actions.lock

@@ -106,7 +106,7 @@ dependencies:
         repo_id: 259445878
     'linux-system-roles/.github@main':
         ref: 'main'
-        commit: 'sha1-038468a64a784796a0202d5c9c714f27ec2cc2c4'
+        commit: 'sha1-cfa9bc3ff2917d6866ad85d1b22b2f32e4a6c210'
         owner_id: 28014670
         repo_id: 320092621
     'sclorg/testing-farm-as-github-action@v4.3.1':

plans/test_playbooks_parallel.fmf

@@ -49,6 +49,43 @@ prepare:
     order: 10
     script: |
       sed -i -e 's|\.lab\.bos\.|.devel.|g' -e 's|\.eng\.bos\.|.devel.|g' /etc/yum.repos.d/*.repo
+  - name: Install package_retry on CentOS 7 and 8
+    how: shell
+    # Generated by Codex model Astra 6 low
+    # Install before EPEL setup and package installation during prepare.
+    order: 5
+    script: |
+      set -eu
+      # shellcheck disable=SC1091
+      . /etc/os-release
+      case "${ID}:${VERSION_ID%%.*}" in
+        centos:7)
+          plugin_dir=/usr/lib/yum-plugins
+          plugin_conf_dir=/etc/yum/pluginconf.d
+          ;;
+        centos:8)
+          # determine system site-packages plugin directory
+          plugin_dir=$(/usr/libexec/platform-python -c 'import sysconfig; print(sysconfig.get_path("purelib") + "/dnf-plugins")')
+          plugin_conf_dir=/etc/dnf/plugins
+          ;;
+        *) exit 0 ;;
+      esac
+      # Pin the latest main-branch commit as of 2026-10-29.
+      revision=cc5725137899d99a3624d88bf491f7e1e455a9d7
+      source_url="https://raw.githubusercontent.com/linux-system-roles/auto-maintenance/${revision}/package_retry"
+      download_dir=$(mktemp -d)
+      trap 'rm -rf "$download_dir"' EXIT
+      for file in package_retry.py package_retry.conf; do
+        curl --fail --location --silent --show-error --retry 5 --retry-delay 5 \
+          --connect-timeout 30 --max-time 120 \
+          --output "$download_dir/$file" "$source_url/$file"
+      done
+      install -d -m 0755 "$plugin_dir" "$plugin_conf_dir"
+      install -m 0644 "$download_dir/package_retry.py" "$plugin_dir/package_retry.py"
+      # Retry after 5, 10, 20, 40, and 80 seconds.
+      sed -i -e 's/^retries = .*/retries = 5/' \
+        -e 's/^strategy = .*/strategy = exponential/' "$download_dir/package_retry.conf"
+      install -m 0644 "$download_dir/package_retry.conf" "$plugin_conf_dir/package_retry.conf"
 discover:
   - name: Prepare managed node
     how: fmf