So I tried this https://github.com/adamralph/scriptcs/commit/da72439397c98ef81f271ffc9b3f4f5c0d25ae1d

but I get 

> Unhandled Exception: System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
>    at System.Collections.Generic.Dictionary`2.get_Item(TKey key)
>    at ScriptCs.Hosting.ScriptServicesBuilder.Build() in c:\code\scriptcs\src\ScriptCs.Hosting\ScriptServicesBuilder.cs:line 39
>    at ScriptCs.Command.CommandFactory.CreateCommand(ScriptCsArgs args, String[] scriptArgs) in c:\code\scriptcs\src\ScriptCs\Command\CommandFactory.cs:line 61
>    at ScriptCs.Program.Main(String[] args) in c:\code\scriptcs\src\ScriptCs\Program.cs:line 19

because no engine is registered. Am I still blundering around incorrectly?