## Bug description

There seems to be an issue with `get_available_timezones_with_offsets`, not sure at what point it broke.

```
Traceback (most recent call last):
    response = view_func(request, *args, **kwargs)
  File "/posthog/posthog/views.py", line 184, in preflight_check
    "available_timezones": get_available_timezones_with_offsets(),
    raise NonExistentTimeError(dt)
```

## Expected behavior
Preflight should work and the timezone list be returned correctly.


## How to reproduce

1. Just check `/_preflight` request

## Environment

- [X] PostHog Cloud
- [ ] self-hosted PostHog, version/commit: _please provide_

## Additional context

Tagging @Twixes as you have more context on this.

#### *Thank you* for your bug report – we love squashing them!

posthog/utils.py
"""
    Returns the symbolic name of the current active branch. Will return None in case of failure.
    Example: get_git_branch()
        => "master"
    """
    try:
        return (
            subprocess.check_output(["git", "rev-parse", "--symbolic-full-name", "--abbrev-ref", "HEAD"])
            .decode("utf-8")
            .strip()
        )
    except Exception:
        return None
def get_git_commit() -> Optional[str]:
    """
    Returns the short hash of the last commit.
    Example: get_git_commit()
        => "4ff54c8d"
    """
    try:
        return subprocess.check_output(["git", "rev-parse", "--short", "HEAD"]).decode("utf-8").strip()
    except Exception:
        return None
def render_template(template_name: str, request: HttpRequest, context: Dict = {}) -> HttpResponse: