eth: when snap is complaining for missing eth, be verbose about the details (#28249)

* eth: when snap is complaining for missing eth, be verbost about the details

* eth: lower snapshot registration error verbosity

eth/handler.go

@@ -462,7 +462,7 @@ func (h *handler) runSnapExtension(peer *snap.Peer, handler snap.Handler) error
 				snap.EgressRegistrationErrorMeter.Mark(1)
 			}
 		}
-		peer.Log().Warn("Snapshot extension registration failed", "err", err)
+		peer.Log().Debug("Snapshot extension registration failed", "err", err)
 		return err
 	}
 	return handler(peer)

eth/peerset.go

@@ -18,6 +18,7 @@ package eth
 
 import (
 	"errors"
+	"fmt"
 	"math/big"
 	"sync"
 
@@ -74,7 +75,7 @@ func (ps *peerSet) registerSnapExtension(peer *snap.Peer) error {
 	// Reject the peer if it advertises `snap` without `eth` as `snap` is only a
 	// satellite protocol meaningful with the chain selection of `eth`
 	if !peer.RunningCap(eth.ProtocolName, eth.ProtocolVersions) {
-		return errSnapWithoutEth
+		return fmt.Errorf("%w: have %v", errSnapWithoutEth, peer.Caps())
 	}
 	// Ensure nobody can double connect
 	ps.lock.Lock()