Improve ErrNotFound

Work with ipld.ErrNotFounds.

go.mod

@@ -3,15 +3,15 @@ module github.com/ipfs/go-merkledag
 require (
 	github.com/gogo/protobuf v1.3.1
 	github.com/ipfs/go-block-format v0.0.2
-	github.com/ipfs/go-blockservice v0.1.0
-	github.com/ipfs/go-cid v0.0.3
-	github.com/ipfs/go-datastore v0.3.1
-	github.com/ipfs/go-ipfs-blockstore v0.1.0
-	github.com/ipfs/go-ipfs-exchange-offline v0.0.1
+	github.com/ipfs/go-blockservice v0.1.4-0.20200407214602-071562482bcf
+	github.com/ipfs/go-cid v0.0.5
+	github.com/ipfs/go-datastore v0.4.4
+	github.com/ipfs/go-ipfs-blockstore v1.0.1-0.20200407212108-882f63676be9
+	github.com/ipfs/go-ipfs-exchange-offline v0.0.2-0.20200407220152-ef546a7fe3f1
 	github.com/ipfs/go-ipfs-util v0.0.1
 	github.com/ipfs/go-ipld-cbor v0.0.3
-	github.com/ipfs/go-ipld-format v0.0.2
-	github.com/multiformats/go-multihash v0.0.10
+	github.com/ipfs/go-ipld-format v0.1.0
+	github.com/multiformats/go-multihash v0.0.13
 )
 
 go 1.12