Improve README.chromium for WPTServe.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/servers/wptserve.py

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Start and stop the WPTserve servers as they're used by the layout tests."""
 
+import datetime
+import logging
 from webkitpy.layout_tests.servers import server_base
 
 
 class WPTServe(server_base.ServerBase):
 
     def __init__(self, port_obj, output_dir):
         super(WPTServe, self).__init__(port_obj, output_dir)
         # These ports must match wpt_support/wpt.config.json
         http_port, http_alt_port, https_port = (8001, 8081, 8444)
         ws_port, wss_port = (9001, 9444)
@@ skipping 26 matching lines @@
             start_cmd += ['--ws_doc_root', path_to_ws_handlers]
 
         self._stdout = self._stderr = self._executive.DEVNULL
         # TODO(burnik): We should stop setting the CWD once WPT can be run without it.
         self._cwd = path_to_wpt_root
         self._env = port_obj.host.environ.copy()
         self._env.update({'PYTHONPATH': path_to_thirdparty})
         self._keep_process_reference = True
         self._start_cmd = start_cmd
 
+        expiration_date = datetime.date(2025, 1, 4)
+        if datetime.date.today() > expiration_date - datetime.timedelta(30):
+            logging.getLogger(__name__).error(
+                'Pre-generated keys and certificates are going to be expired at %s.'
+                ' Please re-generate them by following steps in %s/README.chromium.'
+                % (expiration_date.strftime('%b %d %Y'), path_to_wpt_support))
+
     def _stop_running_server(self):
         # Clean up the pid file.
         if self._pid and not self._executive.check_running_pid(self._pid):
             self._filesystem.remove(self._pid_file)
             return
 
         # TODO(burnik): Figure out a cleaner way of stopping wptserve.
         if self._platform.is_win():
             self._executive.kill_process(self._pid)
         else:
             self._executive.interrupt(self._pid)
 
         # According to Popen.wait(), this can deadlock when using stdout=PIPE and/or stderr=PIPE.
         # We're using DEVNULL for both so that should not occur.
         self._process.wait()