post_gen_project hook script fails upon attempting to create new extension

[felixk4]

Even though I use the docker install, I get the exact same error as described in this issue from someone who installed ckan from source:

Traceback (most recent call last):
  File "/tmp/tmpqq3axb1k.py", line 88, in <module>
    "_checkout": null,
NameError: name 'null' is not defined
Stopping generation because post_gen_project hook script didn't exit successfully
Traceback (most recent call last):
  File "/usr/local/bin/ckan", line 8, in <module>
    sys.exit(ckan())
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1157, in __call__
    return self.main(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1078, in main
    rv = self.invoke(ctx)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1688, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 1434, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/lib/python3.10/site-packages/click/core.py", line 783, in invoke
    return __callback(*args, **kwargs)
  File "/srv/app/src/ckan/ckan/cli/generate.py", line 114, in extension
    cookiecutter(template_loc, no_input=True, extra_context=context,
  File "/usr/local/lib/python3.10/site-packages/cookiecutter/main.py", line 182, in cookiecutter
    result = generate_files(
  File "/usr/local/lib/python3.10/site-packages/cookiecutter/generate.py", line 419, in generate_files
    run_hook_from_repo_dir(
  File "/usr/local/lib/python3.10/site-packages/cookiecutter/hooks.py", line 157, in run_hook_from_repo_dir
    run_hook(hook_name, project_dir, context)
  File "/usr/local/lib/python3.10/site-packages/cookiecutter/hooks.py", line 140, in run_hook
    run_script_with_context(script, project_dir, context)
  File "/usr/local/lib/python3.10/site-packages/cookiecutter/hooks.py", line 123, in run_script_with_context
    run_script(temp.name, cwd)
  File "/usr/local/lib/python3.10/site-packages/cookiecutter/hooks.py", line 94, in run_script
    raise FailedHookException(
cookiecutter.exceptions.FailedHookException: Hook script failed (exit status: 1)

According to this commit, the Cookicutter 2.6 update caused a problem and it seems like that was fixed by making some changes to post_gen_project.py, but when I build the containers and take a look inside, I get the pre-fix post_gen_project.py file with the whole 'context = {{ cookiecutter | jsonify }}' thing and if I manually alter that file according to the fix I can create a new extension without any problems. Is there something wrong on my end or was the fix just not adopted by ckan-docker?