Use the json marshalling when returning Backend_error_with_backtrace

Signed-off-by: David Scott <dave.scott@citrix.com>

Author: David Scott

main.ml

@@ -42,18 +42,10 @@ let backend_error name args =
   Exception.rpc_of_exnty exnty
 
 let backend_backtrace_error name args error =
-  match List.zip error.files error.lines with
-  | None -> backend_error "SCRIPT_FAILED" [ "malformed backtrace in error output" ]
-  | Some pairs ->
-    let backtrace =
-      pairs
-      |> List.map ~f:(fun (filename, line) -> { B.Interop.filename; line })
-      |> B.Interop.to_backtrace
-      |> B.sexp_of_t
-      |> Sexplib.Sexp.to_string in
-    let open Storage_interface in
-    let exnty = Exception.Backend_error_with_backtrace(name, backtrace :: args) in
-    Exception.rpc_of_exnty exnty
+  let error = rpc_of_error error |> Jsonrpc.to_string in
+  let open Storage_interface in
+  let exnty = Exception.Backend_error_with_backtrace(name, error :: args) in
+  Exception.rpc_of_exnty exnty
 
 let missing_uri () =
   backend_error "MISSING_URI" [ "Please include a URI in the device-config" ]