After an upgrade from 2.9.2 to 2.10.2 the site was working normally in the browser, and the system login page accepted credentials. After that was a white screen.
Turning on error logging in admin.php produced the following error:
A Database Error Occurred
Error Number: 1054
Unknown column 'login_state' in 'field list'
SELECT
member_id
,admin_sess
,last_activity
,fingerprint
,sess_start
,login_state
FROM (exp_sessions
) WHEREsession_id
= 'b0e0c13fd814f8ce72c88a242ac269705f9c5df5'Filename: libraries/Session.php
Line Number: 731
The database table exp_update_log indicates successful update to v2.10.2