The compute-side telnet_forward (and vnc_forward) let the
WebSocketDisconnect that starlette raises from send_bytes once the peer
is gone escape to the generic task-exception handler. Its str() is
empty, so every client disconnect during active node output logged a
message-less warning:
WARNING gns3server.compute.base_node:658 Exception while forwarding
WebSocket data to TELNET server:
Catch WebSocketDisconnect in both forwarders and log it at INFO as the
normal end of a session, and format the remaining task exceptions with
!r so their type stays visible. Mirrors the controller-side fix for
the same scenario (2324dcd74).