make everything build again after ByteString Key changes

Backend/Utilities.hs

@@ -1,6 +1,6 @@
 {- git-annex backend utilities
  -
- - Copyright 2012 Joey Hess <id@joeyh.name>
+ - Copyright 2012-2019 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU GPL version 3 or higher.
  -}
@@ -10,17 +10,19 @@ module Backend.Utilities where
 import Annex.Common
 import Utility.Hash
 
+import qualified Data.ByteString as S
+
 {- Generates a keyName from an input string. Takes care of sanitizing it.
  - If it's not too long, the full string is used as the keyName.
  - Otherwise, it's truncated, and its md5 is prepended to ensure a unique
  - key. -}
-genKeyName :: String -> String
+genKeyName :: String -> S.ByteString
 genKeyName s
 	-- Avoid making keys longer than the length of a SHA256 checksum.
-	| bytelen > sha256len =
+	| bytelen > sha256len = encodeBS' $
 		truncateFilePath (sha256len - md5len - 1) s' ++ "-" ++ 
 			show (md5 (encodeBL s))
-	| otherwise = s'
+	| otherwise = encodeBS' s'
   where
 	s' = preSanitizeKeyName s
 	bytelen = length (decodeW8 s')