IDLE should exit if it fails to connect with the execution server
subprocess.  Currently it opens a dead shell window.
diff --git a/Lib/idlelib/PyShell.py b/Lib/idlelib/PyShell.py
index d89802c..e3605ac 100644
--- a/Lib/idlelib/PyShell.py
+++ b/Lib/idlelib/PyShell.py
@@ -340,7 +340,7 @@
                                                     + ", retrying..."
         else:
             display_port_binding_error()
-            return
+            sys.exit()
         # Accept the connection from the Python execution server
         self.rpcclt.accept()
         self.rpcclt.register("stdin", self.tkconsole)