Description of problem:

When installing using a kickstart and a broken "repo" is specified, the installation fails as "[!] Installation source" but no error pops up to help the admin understand what is going on.

Only checking for ERR in /tmp/anaconda.log can give some tip:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
13:10:33,848 DBG payload: retrieving treeinfo from http://192.168.122.1/rhel82 (proxy: ; sslverify: True)
13:10:33,854 DBG payload: getting release version from tree at http://192.168.122.1/rhel82 (8.2)
13:10:33,855 DBG payload: using treeinfo release version of 8.2
13:10:36,207 ERR payload: PayloadError: Failed to download metadata for repo 'BaseOS': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried

13:10:36,207 DBG payload: Updating payload thread state: -1
13:10:36,210 DBG payload: getting release version from tree at None (8.2)
13:10:36,210 DBG payload: using default release version of 8.2
13:10:37,058 DBG payload: Source http://192.168.122.1/rhel82 needs network for installation
13:10:37,100 DBG payload: Source http://192.168.122.1/rhel82 needs network for installation
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

In the example above, an invalid "BaseOS" repo was specified, this leads to the error, but due to the last lines being "Source http://192.168.122.1/rhel82 needs network for installation" (a path to a DVD mounted on HTTP), the admin can believe there is an issue with the Network configuration instead.

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

anaconda-29.19.2.17-1.el8

How reproducible:

Always

Steps to Reproduce:
1. Boot over the network with a kickstart referring to an invalid repository

Excerpt:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
repo --name="Dummy" --baseurl=file://non/existent
url --url=http://192.168.122.1/rhel82
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Actual results:

Starting installer, one moment...
anaconda 29.19.2.17-1.el8 for Red Hat Enterprise Linux 8.2 started.

• installation log files are stored in /tmp during the installation
• shell is available on TTY2
• if the graphical installation interface fails to start, try again with the
  inst.text bootoption to start text installation
• when reporting a bug add logs from /tmp as separate text/plain attachments
  13:17:51 Not asking for VNC because of an automated install
  13:17:51 Not asking for VNC because text mode was explicitly asked for in kickstart
  Starting automated install..
  Generating updated storage configuration
  Checking storage configuration...

================================================================================

================================================================================
Installation

1) [x] Language settings 2) [x] Time settings
(English (United States)) (America/New_York timezone)
3) [!] Installation source 4) [!] Software selection
(Error setting up software (Error checking software
source) selection)

...

Expected results:

Some error message explaining the issue.