None of the python stuff is needed

dev/docker/gcov/Dockerfile

@@ -2,7 +2,7 @@
 
 FROM ubuntu:20.04
 
-RUN apt-get -y -m update && DEBIAN_FRONTEND=noninteractive apt-get install -y cmake python3-numpy g++ gfortran git zip python3-six nano python3-pip gcovr ninja-build
+RUN apt-get -y -m update && DEBIAN_FRONTEND=noninteractive apt-get install -y cmake g++ git zip nano gcovr ninja-build
 
 # This ADD block forces a build (invalidates the cache) if the git repo contents have changed, otherwise leaves it untouched.
 # See https://stackoverflow.com/a/39278224