Description of problem:
When installing over the network behind a firewall, proxy can be set but seems not to function.

Version-Release number of selected component (if applicable):
20-Beta-TC4

How reproducible:
Everytime

Steps to Reproduce:
1. Start Fedora installtion behind a firewall
2. From the central pane got the 'Installation source' windows
3. Select "Closest mirror" and hit 'Proxy'-button
4. Enable proxy and give a proxy address
5. Click 'Done' and watch Installation source status

Actual results:
Installation source status becomes 'Error setting up software source'

Expected results:
Anaconda should fetch mirror data through the proxy and retrieve repo data

Additional info:
I can not find any entry in the logs that reports the proxy settings.