Fwd: pgAdmin4.15: 500 Internal Server Error

I have to add that the application is working in desktop mode

---------- Forwarded message ---------
From: bw <bwakkie(at)gmail(dot)com>
Date: Sat, 30 Nov 2019 at 12:36
Subject: pgAdmin4.15: 500 Internal Server Error
To: pgadmin-support(at)postgresql(dot)org <pgadmin-support(at)postgresql(dot)org>

Pgadmin4 isn't working after upgrading to 4.15
(Was working before the update in server mode on wcgi)

I set the following in config.py:
DEBUG = True
CONSOLE_LOG_LEVEL = logging.DEBUG
FILE_LOG_LEVEL = logging.DEBUG
I restarted apache2
Visiting 127.0.0.1/pgadmin4 gave the attached pgadmin4.log

My system:
Ubuntu 19.04 with the postgresql apps from apt.postgresql.org

Installed packages:
pgadmin4-(apache2,common,dbgsym,doc) 4.15-1.pgdg19.04+1

Any help appreciated,

Regards,

Bastiaan