Raspberry PI Core installation - Problem with pip


I´m new to homeassistant and trying to install this on a Raspberry PI with the core method.

I worked through the steps and get stuck when I have to install wheel.

pip throws the error message:
WARNING: pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.

I have tried to install some packages a suggested under the link below, but it didnt help.

What do I have to do?