Update contributing chapter

Fix and update the information how to contribute. Due to
the latest changes in tox.ini some requirements regarding
the tox and python versions came up. This commit updates
the docs in this regard

doc/source/contributing.rst

@@ -45,59 +45,70 @@ Install Required Operating System Packages
 ------------------------------------------
 
 {kiwi} requires the following additional packages which are not provided by
-:command:`pip`:
+:command:`pip`. Those will be installed by calling the
+`install_devel_packages.sh` helper script from the checked out Git
+repository as follows:
+
+.. code:: shell-session
+
+   $ sudo helper/install_devel_packages.sh
+
+.. note::
+
+   The helper script checks for the package managers `zypper` and
+   `dnf` and associates a distribution with it. If you use a
+   distribution that does not use one of those package managers
+   the script will not install any packages and exit with an
+   error message. In this case we recommend to take a look at
+   the package list encoded in the script and adapt to your
+   distribution and package manager as needed. Because distributions
+   also changes on a regular basis it might happen that the
+   `install_devel_packages` helper is not 100% accurate or outdated
+   depending on your host system. In this case the following
+   list describes the needed components and we are happy to
+   received feedback or patches to make `install_devel_packages`
+   a better experience.
 
 XML processing libraries
   `libxml2` and `libxslt` (for :mod:`lxml`)
 
 Python header files, GCC compiler and glibc-devel header files
   Required for python modules that hooks into shared library context
+  and often named similar to: `python3-devel`
 
 Spell Checking library
   Provided by the `enchant` library
 
 ShellCheck
   `ShellCheck <https://github.com/koalaman/shellcheck>`_ script linter.
 
-ISO creation program
-  One of ``xorriso`` (preferred) or ``genisoimage``.
+ISO creation program `xorriso`.
 
 LaTeX documentation build environment
   A full LaTeX installation is required to build the PDF documentation
   [#f1]_.
 
 Host Requirements To Build Images
-  A full set of tools needed to build images and provided by
+  A set of tools needed to build images and provided by
   the `kiwi-systemdeps` package
 
-The above mentioned system packages will be installed by calling the
-`install_devel_packages.sh` helper script from the checked out Git
-repository as follows:
-
-.. code:: shell-session
-
-   $ sudo helper/install_devel_packages.sh
-
-.. note::
-
-   The helper script checks for the package managers `zypper` and
-   `dnf` and associates a distribution with it. If you use a
-   distribution that does not use one of those package managers
-   the script will not install any packages and exit with an
-   error message. In this case we recommend to take a look at
-   the package list encoded in the script and adapt to your
-   distribution and package manager as needed.
-
 Create a Python Virtual Development Environment
 -----------------------------------------------
 
 The following commands initializes and activates a development
 environment for Python 3:
 
+.. note::
+
+   {kiwi} uses tox to create a devel environment and to run
+   tests, linters and other tasks in the tox generated environment.
+   A tox version >= 3.3 is required for this setup process. On your
+   host a python version >= 3.7 is required for tox to work.
+
 .. code:: shell-session
 
    $ tox -e devel
-   $ source .tox/3/bin/activate
+   $ source .tox/devel/bin/activate
 
 The commands above automatically creates the application script
 called :command:`kiwi-ng`, which allows you to run {kiwi} from the
@@ -115,7 +126,7 @@ Python sources inside the virtual environment:
 
    .. code:: shell-session
 
-      $ sudo $PWD/.tox/3/bin/kiwi-ng system build ...
+      $ sudo $PWD/.tox/devel/bin/kiwi-ng system build ...
 
 To leave the development mode, run:
 
@@ -127,8 +138,7 @@ To resume your work, :command:`cd` into your local Git repository and call:
 
 .. code:: shell-session
 
-    $ source .tox/3/bin/activate
-
+    $ source .tox/devel/bin/activate
 
 Alternatively, you can launch single commands inside the virtualenv without
 sourcing it directly:
@@ -158,7 +168,7 @@ enabled via:
 
 .. code:: shell-session
 
-    $ tox "-n NUMBER_OF_PROCESSES"
+    $ tox -- "-n NUMBER_OF_PROCESSES"
 
 where you can insert an arbitrary number as `NUMBER_OF_PROCESSES` (or a
 shell command like `$(nproc)`). Note that the double quotes around `-n
@@ -176,11 +186,11 @@ If you want to see the available targets, use the option `-l` to let
     $ tox -l
 
 To only run a special target, use the `-e` option. The following
-example runs the test cases for the Python 3.6 interpreter only:
+example runs the test cases for the Python 3.11 interpreter only:
 
 .. code:: shell-session
 
-    $ tox -e unit_py3_6
+    $ tox -e unit_py3_11
 
 
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