mcr.microsoft.com/devcontainers/base:ubuntu seems to have invalid /etc/timezone value "/UTC"

[epicwhale]

The Ubuntu variant of the base devcontainer image sets /etc/timezone to /UTC (with leading slash) instead of Etc/UTC. This breaks Python's zoneinfo module and any library that reads system timezone (e.g., Pendulum, Prefect).

Reproduction:
docker run --rm mcr.microsoft.com/devcontainers/base:ubuntu cat /etc/timezone

Output: /UTC

Expected: Etc/UTC or UTC

Actual: /UTC

Error:

  from zoneinfo import ZoneInfo
  ZoneInfo('/UTC')
  # ValueError: ZoneInfo keys may not be absolute paths, got: /UTC

oddly, using :debian variant doesn't have the same issue