spinnaker: "Unable to locate package spinnaker-igor" during `hal deploy apply` on Ubuntu 14.04 docker image

Environment

I am running hal 0.42.0-20180302093153 inside a docker image with Ubuntu 14.04.5 LTS (ubuntu:14.04). Halyard is installed via https://raw.githubusercontent.com/spinnaker/halyard/master/install/debian/InstallHalyard.sh during the build phase of the (custom) docker image. The rest of the hal configuration is then run in the entrypoint.

Description

Expected behaviour: hal deploy apply finishes gracefully / finds the spinnaker-igor package.

Actual behaviour: hal deploy apply exits with error Unable to locate package spinnaker-igor

Note that the apply deployment phase seems to have finished at this point. Actual output is like this:

[... settings and prep successes]
^ Apply deployment
[... lots more apply deployments]
+ Apply deployment
  Success
+ Run `hal deploy connect` to connect to Spinnaker.
Updating apt package lists...
[... lots of packages]
E: Unable to locate package spinnaker-igor
! ERROR Error encountered running script. See above output for more
  details.

(full output: https://gist.github.com/surculus12/6eb9f103026d0e32ec10d537e4a6783e)

Steps to Reproduce

Dockerfile: https://gist.github.com/surculus12/6bc3d7a7fda6d6c6e3d356f6c189c76b entrypoint.sh: https://gist.github.com/surculus12/94c25ddba522917ad2c6c56ce7209b2e

Additional Details

Also tried hal version 1.5.4.

All similar issues I’ve found have to do with Ubuntu 16.04, where downgrading to 14.04 solved the issue.