Update the base image.

Dockerfile

-FROM registry.hub.docker.com/library/python:3.9-slim-buster as wheels
+FROM registry.hub.docker.com/library/python:3.10-slim-bullseye as wheels
 # hadolint ignore=DL3008,DL3015
 RUN apt-get update && \
     DEBIAN_FRONTEND=noninteractive apt-get install -y \
@@ -11,7 +11,7 @@ WORKDIR /wheels
 RUN python3 -m pip wheel https://github.com/python-ldap/python-ldap/releases/download/python-ldap-3.3.1/python-ldap-3.3.1.tar.gz
 RUN python3 -m pip wheel git+https://github.com/adarnimrod/flask-simpleldap.git@ldapi-support#egg=flask-simpleldap
 
-FROM registry.hub.docker.com/library/python:3.9-slim-buster
+FROM registry.hub.docker.com/library/python:3.10-slim-bullsye
 # hadolint ignore=DL3008
 RUN apt-get update && \
     DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \