Fix #2854: crash if Ndiff exits with error status

zenmap/zenmapCore/Diff.py

@@ -133,7 +133,7 @@ class NdiffCommand(subprocess.Popen):
                 command_list,
                 universal_newlines=True,
                 stdout=self.stdout_file,
-                stderr=self.stdout_file,
+                stderr=subprocess.PIPE,
                 env=env,
                 shell=(sys.platform == "win32")
                 )

zenmap/zenmapGUI/DiffCompare.py

@@ -377,6 +377,7 @@ class DiffWindow(Gtk.Window):
                 error_text = _(
                     "The ndiff process terminated with status code %d."
                     ) % status
+                if self.ndiff_process.stderr:
                     stderr = self.ndiff_process.stderr.read()
                     if len(stderr) > 0:
                         error_text += "\n\n" + stderr