show some context on this error

Author: VictorTaelin

src/HVML/Inject.hs

@@ -130,7 +130,7 @@ doInjectCoreAt book core host argList = do
         else do
           return $ m
       Nothing -> do
-        error $ "Unbound variable: " ++ name)
+        error $ "Unbound variable: \n\x1b[2m" ++ name ++ "\n\x1b[0mIn term:\n\x1b[2m" ++ Data.List.take 256 (coreToString core) ++ "...\x1b[0m")
     (args state)
     (vars state)
   got host