fetchnuget: improve "multiple hashes" error message

pkgs/build-support/dotnet/fetchnuget/default.nix

@@ -1,4 +1,5 @@
 {
+  lib,
   fetchurl,
   buildDotnetPackage,
   unzip,
@@ -14,10 +15,12 @@ attrs@{
   ...
 }:
 if md5 != "" then
-  throw "fetchnuget does not support md5 anymore, please use 'hash' attribute with SRI hash"
+  throw "fetchnuget does not support md5 anymore, please use 'hash' attribute with SRI hash: ${
+    lib.generators.toPretty { } attrs
+  }"
 # This is also detected in fetchurl, but we just throw here to avoid confusion
 else if (sha256 != "" && hash != "") then
-  throw "multiple hashes passed to fetchNuGet"
+  throw "multiple hashes passed to fetchNuGet: ${lib.generators.toPretty { } url}"
 else
   buildDotnetPackage (
     {