ceph-mgr spews unexpected errors when loading modules, like this (for ~every module):

2025-04-23T21:33:16.119+0900 ffff902f4040  1 mgr[py] Loading python module 'prometheus'
2025-04-23T21:33:16.235+0900 ffff902f4040  4 mgr[py] load_subclass_of: found class: 'prometheus.Module'
2025-04-23T21:33:16.235+0900 ffff902f4040 -1 mgr[py] Module prometheus has missing NOTIFY_TYPES member
2025-04-23T21:33:16.235+0900 ffff902f4040 -1 mgr[py] Module not found: 'mgr_module'
2025-04-23T21:33:16.235+0900 ffff902f4040 -1 mgr[py] AttributeError: type object 'Module' has no attribute 'NOTIFY_TYPES'

2025-04-23T21:33:16.235+0900 ffff902f4040  4 mgr[py] Standby mode not provided by module 'prometheus'

The `Module not found` for mgr_module in particular is suspicious.

Note that prometheus *does* provide a standby mode, so this is broken (and breaks the functionality that standby mgrs can still be scraped). 

This is after uninstalling `ceph-mgr-diskprediction-local` to work around bug 2307587.

This is a regression from F40.

Reproducible: Always