P-chain: Improve GetValidatorsSet error expressivity (#2808)

Co-authored-by: Stephen Buttolph <[email protected]>

vms/platformvm/validators/manager.go

@@ -5,11 +5,11 @@ package validators
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"time"
 
 	"github.com/ava-labs/avalanchego/cache"
-	"github.com/ava-labs/avalanchego/database"
 	"github.com/ava-labs/avalanchego/ids"
 	"github.com/ava-labs/avalanchego/snow/validators"
 	"github.com/ava-labs/avalanchego/utils/constants"
@@ -30,7 +30,11 @@ const (
 	recentlyAcceptedWindowTTL     = 2 * time.Minute
 )
 
-var _ validators.State = (*manager)(nil)
+var (
+	_ validators.State = (*manager)(nil)
+
+	errUnfinalizedHeight = errors.New("failed to fetch validator set at unfinalized height")
+)
 
 // Manager adds the ability to introduce newly accepted blocks IDs to the State
 // interface.
@@ -247,7 +251,12 @@ func (m *manager) makePrimaryNetworkValidatorSet(
 		return nil, 0, err
 	}
 	if currentHeight < targetHeight {
-		return nil, 0, database.ErrNotFound
+		return nil, 0, fmt.Errorf("%w with SubnetID = %s: current P-chain height (%d) < requested P-Chain height (%d)",
+			errUnfinalizedHeight,
+			constants.PrimaryNetworkID,
+			currentHeight,
+			targetHeight,
+		)
 	}
 
 	// Rebuild primary network validators at [targetHeight]
@@ -295,7 +304,12 @@ func (m *manager) makeSubnetValidatorSet(
 		return nil, 0, err
 	}
 	if currentHeight < targetHeight {
-		return nil, 0, database.ErrNotFound
+		return nil, 0, fmt.Errorf("%w with SubnetID = %s: current P-chain height (%d) < requested P-Chain height (%d)",
+			errUnfinalizedHeight,
+			subnetID,
+			currentHeight,
+			targetHeight,
+		)
 	}
 
 	// Rebuild subnet validators at [targetHeight]

vms/platformvm/warp/validator.go

@@ -55,7 +55,7 @@ func GetCanonicalValidatorSet(
 	// Get the validator set at the given height.
 	vdrSet, err := pChainState.GetValidatorSet(ctx, pChainHeight, subnetID)
 	if err != nil {
-		return nil, 0, fmt.Errorf("failed to fetch validator set (P-Chain Height: %d, SubnetID: %s): %w", pChainHeight, subnetID, err)
+		return nil, 0, err
 	}
 
 	var (