Need to redirect when permission issue happened on CiviCRM Page
You can do this by specifying your custom Fatal Error Handler at Administer -&gt; System Settings -&gt; Debugging and Error Handling. 


Enter the name of the function eg myCustomErrorHandler for Fatal Error Handler input field.
Define this function in one of the extension .php file. The param should hold the message of the error and if it matches the permission text msg, you can use redirect function to navigate to the login page. Eg.

function myCustomErrorHandler($params) {
  if ($params['message'] == 'error message') {
    CRM_Utils_System::redirect($urlyouwant);
  }
  return FALSE;
}

Note the return statement in this function. FALSE is required to call the default error handler in case your function wasn't able to do the needful.
return TRUE; will not call the default Error handler in CiviCRM.