topology: inline into string literal

Author: mwarning

topology.py

@@ -288,7 +288,7 @@ def plus(id):
     elif args.topology == 'nodes':
         output = create_nodes(args.count)
     else:
-        eprint('Unknown topology: {}'.format(args.topology))
+        eprint(f'Unknown topology: {args.topology}')
         exit(1)
 
     for link in output['links']: