DOC: Add hint for Python package development

docs/guidelines/makefile.rst

@@ -63,6 +63,19 @@ Install Targets
 | ``install`` | Install the project or package                                                |
 +-------------+-------------------------------------------------------------------------------+
 
+.. hint::
+
+    You can also install dependent Python packages locally without depending on the :ref:`PyPi Server`.
+    Simply clone the Git repository of the dependent Python package and use one of the following commands **while the project's Python venv is active**:
+
+    .. code-block:: bash
+
+        # Install Python package for the use in a project.
+        make -C {local Git repository} install
+
+        # Develop on a Python package while in use in a project (i.e. library development).
+        make -C {local Git repository} develop
+
 .. hint::
 
     In case you're not in our private networks, installing PyPi packages might fail because our :ref:`PyPi Server` is not available publicly. In this case, you can often overwrite the ``PYPI_INDEX`` like this: