[bench/client] fix mutation during iteration bug

bench/client.py

@@ -124,15 +124,16 @@ def run_remote_clients(cmd: str, out: Path, err: Path, csv: Path,
 
     for host in hosts:
         # prepend out files with the host the client runs on
-        out = out.parent / f'{host}-{out.name}'
-        err = err.parent / f'{host}-{err.name}'
-        csv = csv.parent / f'{host}-{csv.name}'
+        h_out = out.parent / f'{host}-{out.name}'
+        h_err = err.parent / f'{host}-{err.name}'
+        h_csv = csv.parent / f'{host}-{csv.name}'
 
-        files.extend([out, err, csv])
+        files.extend([h_out, h_err, h_csv])
 
-        cmd = cmd.format(outfile=csv)
+        h_cmd = cmd.format(outfile=h_csv)
 
-        clients.append(Client(cmd, out, err, remote_cmd=remote_cmd, host=host))
+        clients.append(
+            Client(h_cmd, h_out, h_err, remote_cmd=remote_cmd, host=host))
 
     # await all clients
     for client in clients: