frequencies: UnboundLocalError: local variable 'weights_attribute' referenced before assignment

[joverlee521]

Error seen in private seasonal flu build.

[batch] [2024-02-13T14:17:13-08:00] Traceback (most recent call last):
[batch] [2024-02-13T14:17:13-08:00]   File "/nextstrain/augur/augur/__init__.py", line 66, in run
[batch] [2024-02-13T14:17:13-08:00]     return args.__command__.run(args)
[batch] [2024-02-13T14:17:13-08:00]   File "/nextstrain/augur/augur/frequencies.py", line 129, in run
[batch] [2024-02-13T14:17:13-08:00]     if weights_attribute:
[batch] [2024-02-13T14:17:13-08:00] UnboundLocalError: local variable 'weights_attribute' referenced before assignment
[batch] [2024-02-13T14:17:13-08:00] An error occurred (see above) that has not been properly handled by Augur.
[batch] [2024-02-13T14:17:13-08:00] To report this, please open a new issue including the original command and the error above:
[batch] [2024-02-13T14:17:13-08:00]     <https://github.com/nextstrain/augur/issues/new/choose>

Affected versions

Augur 24.2.0

Workaround

Use Augur <=24.1.0, or <=24.0.0 to avoid #1411. For users of Nextstrain's Docker runtime, NEXTSTRAIN_DOCKER_IMAGE=nextstrain/base:build-20240122T233533Z is the latest image that has Augur 24.0.0.

[victorlin]

This happens when --method diffusion is used with --tree. Will make a PR to fix.

[victorlin]

Pyright (#1246) supposedly has the ability to catch these types of programming errors in CI.