ros_buildfarm prerelease script cannot install package dependency

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I'm getting an error when trying to run a prerelease test for a package:

generate_prerelease_script.py   https://raw.githubusercontent.com/ros-infrastructure/ros_buildfarm_config/production/index.yaml   noetic default ubuntu focal amd64   --custom-repo     linux_networking__custom-2:git:https://github.com/PR2-prime/linux_networking.git:melodic-devel   --level 0   --output-dir ./

I get the following error:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/apt/cache.py", line 299, in __getitem__
    rawpkg = self._cache[key]
KeyError: 'python-twisted-core'

During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/tmp/ros_buildfarm/scripts/devel/create_devel_task_generator.py", line 287, in <module>
    main()
  File "/tmp/ros_buildfarm/scripts/devel/create_devel_task_generator.py", line 150, in main
    get_binary_package_versions(apt_cache, debian_pkg_names_testing))
  File "/tmp/ros_buildfarm/ros_buildfarm/common.py", line 144, in get_binary_package_versions
    pkg = apt_cache[debian_pkg_name]
  File "/usr/lib/python3/dist-packages/apt/cache.py", line 301, in __getitem__
    raise KeyError('The cache has no package named %r' % key)
KeyError: "The cache has no package named 'python-twisted-core'"