Process not exiting, emitting whitespace

gistfile1.cs

  class NugBug
  {

    public static void Help() {
      int timeout = 5000;

      using (Process process = new Process())
      {
        process.StartInfo.FileName = "mono";
        process.StartInfo.Arguments = "--runtime=v4.0 /usr/local/bin/NuGet.exe help";
        process.StartInfo.UseShellExecute = false;
        process.StartInfo.RedirectStandardOutput = true;
        process.StartInfo.RedirectStandardError = true;

        StringBuilder output = new StringBuilder();
        StringBuilder error = new StringBuilder();

        using (AutoResetEvent outputWaitHandle = new AutoResetEvent(false))
        using (AutoResetEvent errorWaitHandle = new AutoResetEvent(false))
        {
          process.OutputDataReceived += (sender, e) => {
            if (e.Data == null)
            {
                outputWaitHandle.Set();
            }
            else
            {
                output.AppendLine(e.Data);
            }
          };
          process.ErrorDataReceived += (sender, e) =>
          {
              if (e.Data == null)
              {
                  errorWaitHandle.Set();
              }
              else
              {
                  error.AppendLine(e.Data);
              }
          };

          process.Start();

          process.BeginOutputReadLine();
          process.BeginErrorReadLine();

          if (process.WaitForExit(timeout) &&
              outputWaitHandle.WaitOne(timeout) &&
              errorWaitHandle.WaitOne(timeout))
          {
              // Process completed. Check process.ExitCode here.
              UnityEngine.Debug.Log("done");
          }
          else
          {
              // Timed out.
              UnityEngine.Debug.Log("timeout");
              UnityEngine.Debug.Log(output);
          }
        }
      }
    }