Cannot install required packages for "8. Cross-compile and Install ROS"

[EntnyJill]

When I try execute command
XCS~$ sudo apt-get install python-rosdep python-rosinstall-generator python-wstool python-rosinstall python-empy
I get an errors:

Package python-empy is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

Package python-rosinstall is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
  python3-rosinstall

Package python-rosinstall-generator is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
  python3-rosinstall-generator

Package python-wstool is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
However the following packages replace it:
  python3-wstool

E: Unable to locate package python-rosdep
E: Package 'python-rosinstall-generator' has no installation candidate
E: Package 'python-wstool' has no installation candidate
E: Package 'python-rosinstall' has no installation candidate
E: Package 'python-empy' has no installation candidate

I tried to install python3 alternatives but execution of command

XCS~$ ./src/catkin/bin/catkin_make_isolated \
     -DCMAKE_BUILD_TYPE=Release \
     -DCMAKE_TOOLCHAIN_FILE=/home/pi/rpicross_notes/rpi-generic-toolchain.cmake

gives me error

ImportError: "from catkin_pkg.topological_order import topological_order" failed: No module named catkin_pkg.cmake
Make sure that you have installed "catkin_pkg", it is up to date and on the PYTHONPATH.

How can I fix it?

[HesselM]

I haven't looked at ROS in a very long time.
I've done a large update to the guide 2 years ago, but only managed to update the guide up till OpenCV. So ROS could be seriously outdated: both because ROS2 has been introduced, because the guide has been updated (and therefore scripts and paths have been updated) and because the Raspberry Pi system underwent several updates.
The only way to fix this is to rewrite and recheck all steps, which is something on the planning, but might take a couple of months before I have time to do this.
In case you (or someone else) has fixed it: feel free to make a PR and/or suggestions!