The old versions of mongodb are blocking py2 cleanup. Please stabilize a newer version and clean them up.
The latest Graylog for example still requires MongoDB 4.0 (https://docs.graylog.org/en/3.2/pages/installation.html):
The Graylog server application has the following prerequisites:
MongoDB 3.6 or 4.0
Or version 4.2 in 4.0 compatibility mode.
Old versions last rited.
Reverted, I've missed stabilization.