make sure hex output is padded properly

lib/Echidna/ABI.hs

@@ -20,6 +20,7 @@ import Data.List (intercalate)
 import Data.List.NonEmpty (NonEmpty)
 import Data.List.NonEmpty qualified as NE
 import Data.Maybe (fromMaybe, catMaybes)
+import Text.Printf (printf)
 import Data.Text (Text)
 import Data.Text qualified as T
 import Data.Text.Encoding (encodeUtf8)
@@ -71,7 +72,7 @@ ppAbiValue = \case
   AbiInt  _ n         -> show n
   AbiAddress n        -> "0x" <> showHex n ""
   AbiBool b           -> if b then "true" else "false"
-  AbiBytes 32 b       -> "0x" <> BS.foldr showHex "" b
+  AbiBytes 32 b       -> "0x" <> (BS.foldr (\x -> (<>) (printf "%02x" x)) "" b)
   AbiBytes _ b        -> show b
   AbiBytesDynamic b   -> show b
   AbiString s         -> show s