leapp fails to install RHEL 8 userspace packages "execv() failed: No such file or directory"

Issue

leapp fails and the leapp-report shows:

Risk Factor: high
Title: Unable to install RHEL 8 userspace packages.
Summary: {"details": "DNF failed to install userspace packages, likely due to the proxy config
uration detected in a repository configuration file.", "stderr": "Failed to create directory /
var/lib/leapp/scratch/mounts/root_/system_overlay//sys/fs/selinux: Read-only file system
Failed to create directory /var/lib/leapp/scratch/mounts/root_/system_overlay//sys/fs/selinux:
 Read-only file system
Host and machine ids are equal (32e04309aa9c47f493e6367969a9f5f4): refusing to link journals
execv() failed: No such file or directory