Bug 1532893 - Retry packages tasks when snapshot.debian.org doesn't respond. r=dustin

Bug 1486071 intended to fix this, but while the tasks are setup to
restart on exit status 100, there are multiple failure cases where
snapshot.debian.org doesn't respond and the exit status is not 100.

One is dget, when downloading package sources from snapshot.debian.org.
Eventually, those should move to fetch tasks, but in the meantime, we
bubble up get errors with an exit code 100.

mk-build-deps wraps a call to apt-get install, but doesn't return the
exit code that apt-get returns when apt-get returns one. It makes it
hard to distinguish the error modes, but mk-build-deps is unlikely to
fail on anything else than apt-get. Not all apt-get failures would be
due to snapshot.debian.org availability, but that's a tradeoff we
decided was okay in bug 1486071.

Differential Revision: https://phabricator.services.mozilla.com/D22269

--HG--
extra : moz-landing-system : lando

taskcluster/taskgraph/transforms/job/debian_package.py

@@ -159,14 +159,14 @@ def docker_worker_debian_package(config, job, taskdesc):
         'apt-get dist-upgrade && '
         'cd /tmp && '
         # Get, validate and extract the package source.
-        'dget -d -u {src_url} && '
+        '(dget -d -u {src_url} || exit 100) && '
         'echo "{src_sha256}  {src_file}" | sha256sum -c && '
         '{unpack} && '
         'cd {package} && '
         # Optionally apply patch and/or pre-build command.
         '{adjust}'
         # Install the necessary build dependencies.
-        'mk-build-deps -i -r debian/control -t \'{resolver}\' && '
+        '(mk-build-deps -i -r debian/control -t \'{resolver}\' || exit 100) && '
         # Build the package
         'DEB_BUILD_OPTIONS="parallel=$(nproc) nocheck" dpkg-buildpackage && '
         # Copy the artifacts