add a hint how to disable the pypi caching proxy

docs/admin-guide/configuration/software/python.md

@@ -76,3 +76,16 @@ For additional information on how to install packages (including `pip`) please c
 ```{note}
 The packages prefixed with `python3-` are for the default Default Python version. For newer versions RedHat has a versioned prefix like `python38-` or `python3.11-`. There might not be for all libraries packages for all availabe Python versions. Then you might need to install your library with `pip`.
 ```
+
+### PYPI Package Caching Proxy
+
+By default all managed RHEL systems at PSI have configured a PYPI package caching proxy (pypi.psi.ch). This proxy is used by default for all `pip` installations on the system.
+
+If you want to disable this behavior you can use the following hiera key:
+
+```yaml
+python::use_pip_cache: false
+```
+
+!!! note 
+    If you once had the caching proxy configured, you might need to manually remove `/etc/pip.conf` to disable the proxy again before you apply this setting.