pgAdmin4.13: failed to launch server

Environment is Ubuntu 18.04, pgAdmin4.13 was loaded from the relevant
ubuntu repository.

This was working previously, changed in the last week.  It could have been
after an install.
I get this message when running from the app icon.
If I run it from the command line in /usr/bin, I get the same error, and
the following is displayed:

Python path:  "python3:/usr/lib/python3/dist-packages"
Python Home:  ""
Webapp path:  "/usr/share/pgadmin4/web/pgAdmin4.py"
"Failed to launch the application server, server thread exiting."
 to launch the application server, server thread exiting."

If I go to /usr/share/pgadmin4/web, and run sudo python3 pgAdmin4.py, then
the server will start and all is working fine...

if I run python3 from the command line in any directory, python3.6.8 starts
up
If I run python from any directory,  python 2.7.15 starts up

Any ideas?