auto.create_or_select_stack(
    stack_name=stack_name,
    work_dir=work_dir,
    opts=auto.LocalWorkspaceOptions(
        project_settings=auto.ProjectSettings(
            name=pulumi_project_name,
            runtime="python",
            backend=auto.ProjectBackend(url=f"s3://{PULUMI_STATE_BUCKET}/{pulumi_state_key}?region={AWS_REGION}&awssdk=v2"),
        ),
    ),
)

Using the above automation API code, I'm getting the following error:

yaml.constructor.ConstructorError: could not determine a constructor for the tag 'tag:<http://yaml.org|yaml.org>,2002:python/object:pulumi.automation._project_settings.ProjectBackend'

Does anyone know why, and/or what I can do to fix this?

not familiar with the automation API, but going with the error message it almost looks like as it says, it cannot infer a constructor for the "ProjectBackend". One way to test this out would be at the REPL. Assuming you have an

import pulumi.automation as auto

(looks like it?):

>>> import pulumi_automation as auto
>>> auto.ProjectBackend # does this give you an error?

If that gives you an error, then we have something to work with. Otherwise, i'd also keep exploring around what's going on with the backend argument

I haven't had much luck finding stuff in the Pulumi Python docs. Instead I usually rely on the type hints in my editor, and browsing the source code (right click > go to definition).

re https://pulumi-community.slack.com/archives/CDE799L1M/p1684329583523479?thread_ts=1684291019.612099&cid=CDE799L1M, you mean browsing the Pulumi source code?

Yup

gotcha. That's a good approach. Thanks! if

auto.ProjectBackend

does not give you an error, I'm afraid I'm at my wits' end... If you can provide a small complete program so others can reproduce it, I think that would help others look at it for you

I worked around the error by using the

PULUMI_BACKEND_URL

environment variable documented here: https://www.pulumi.com/docs/cli/environment-variables/ Ideally using

auto.ProjectBackend

would work, but the env var is good enough for my purposes.