Upload of an image manifest to Reggie failed today with a unique constraint violation. At the time there were two manifest uploads to the same repo:
```
2024-06-06 22:36:07,387 put_manifest(repos/releng/scap/cache/verify-deps-bookworm, master-I218be862c39080e9a8711211dee2786e32b2fae2)
2024-06-06 22:36:07,391 put_manifest(repos/releng/scap/cache/verify-deps-bookworm, master-I68c5d877d833894f7111b82af7a10e8a95a92aee)
```
The relevant part of the stack trace:
```
Traceback (most recent call last):
...
File "/srv/app/app.py", line 529, in put_manifest
manifest_blob = REPOBLOBS.put(repo, request.data)
File "/srv/app/reggie/repo.py", line 44, in put
return self.finish_upload(repo, uuid, offset)
File "/srv/app/reggie/repo.py", line 24, in finish_upload
lock_database_exclusive(self.db_session)
File "/srv/app/reggie/database.py", line 27, in lock_database_exclusive
db_session.flush()
...
```