precise commands to also support hpc systems

docs/users/jupyterlab/4.2/index.md

@@ -82,12 +82,12 @@ One of the standout features of Jupyter-JSC is the flexibility it offers users t
 
 <h3>1. <strong>Install python package</strong></h3>
 ```
-source /tmp/custom/load_jupyter_version.sh # This loads the jupyter environment
+test -f /tmp/custom/load_jupyter_version.sh && source /tmp/custom/load_jupyter_version.sh # Load the jupyter environment, only required on JSC-Cloud
 pip install --user jupyterview # or the extension you would like to install
 ```
 You can check the success with these commands:  
 ```
-source /tmp/custom/load_jupyter_version.sh # This loads the jupyter environment
+test -f /tmp/custom/load_jupyter_version.sh && source /tmp/custom/load_jupyter_version.sh # Load the jupyter environment, only required on JSC-Cloud
 jupyter labextension list
 ```
 > You will find the installed extension in this list. The extension might be listed with the hint "enabled X" instead of "enabled OK", that should be an issue while using the extension.
@@ -110,7 +110,7 @@ If something's not working as expected, you may find additional information in t
 ## Uninstall your own Extensions
 To remove the previously installed extension, you have to set `PYTHONNOUSERSITE` to `0`. Otherwise pip will not look into the locally installed packages. 
 ```
-source /tmp/custom/load_jupyter_version.sh # This loads the jupyter environment
+test -f /tmp/custom/load_jupyter_version.sh && source /tmp/custom/load_jupyter_version.sh # Load the jupyter environment, only required on JSC-Cloud
 PYTHONNOUSERSITE=0 pip uninstall jupyterview
 ```
 After a restart of your JupyterLab, the extension will be fully removed.