anchor.diff:    // opens the web page in the default webbrowser 
     let solution' pathSource pathTarget log =
   
  +    // Check that the files exist
  +    [pathSource ; pathTarget]
  +    |> List.iter(fun path -> 
  +      match File.Exists path with
  +      | true -> ()
  +      | false -> failwith (sprintf "Could not find file %s" path))
  +
       let app' = solutionApp pathSource pathTarget log
   
       let port = 
  
positive.code:       ex -> log.WriteLine(LogLevel.Error,sprintf "%s" ex.Message )
      
    // unpack the solution to a defined folder
    let unpackSolution zip temp (log:ConsoleLogger.ConsoleLogger) = 
  
      let folderName = Guid.NewGuid().ToString()
  
  
negative.code:             |> List.iter(fun x -> nameTreeWalker sw x)
  
      let build pathSource pathTarget (log:ConsoleLogger.ConsoleLogger) = 
        // Check that the files exist
        [pathSource ; pathTarget]
        |> List.iter(fun path -> 
          match File.Exists path with
          | true -> ()
          | false -> failwith (sprintf "Could not find file %s" path))
  
        let root = executingPath
        let csvPath = Path.Combine(root,"diffSummary.csv")
  
  