cannot update anymore: "Failed to obtain the transaction lock (logged in as: root)"

[roberto68]

I want to install system-config packags so I did

 dnf install system-config-*

, dnf downloaded all packages but then instalation failed

Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
Failed to obtain the transaction lock (logged in as: root).
The downloaded packages were saved in cache till the next successful transaction.
You can remove cached packages by executing 'dnf clean packages'.
Error: Could not run transaction.

I did

 dnf clean packages

and then try to install it again but failed to do so.
It seems like a serious bug

[basab]

In my case with same problem is solved by doing following steps:
1. dnf clean all
2. Restart the system.

Thanks