ModuleNotFoundError: No module named 'seaserv'

Upgrading from Pro v8.0.14 to v8.0.16 following maintenance release process of running ./minor-upgrade.sh. Seafile starts fine but on starting Seahub, I get this error:

[root@hobbiton seafile-server-latest]# ./seahub.sh start    

LC_ALL is not set in ENV, set to en_US.UTF-8
Starting seahub at port 8000 ...
Traceback (most recent call last):
  File "/data/seafile/seafile-pro-server-8.0.16/check_init_admin.py", line 19, in <module>
    from seaserv import ccnet_api
ModuleNotFoundError: No module named 'seaserv'

I’ve rolled back to v8.0.14 as this is a production system.

Supplemental information: upgrade from v8.0.14 to v8.0.15 works fine (Seahub starts fine) but same error occurs with upgrade to v8.0.16, i.e. the error occurs in v8.0.16 alone.

Later… this problem doesn’t occur in v8.0.17 which has been released very recently so I’m assuming this was a bug in v8.0.16