socket: Fix a traceback on server restart

I believe there may also be others.  I'm still not sure why clients would be
sending open requests without session or csrf values in their cookies, though.

(imported from commit 7e9660c1c4d5c2abf55ff21b433ba0117180eb82)

zerver/lib/socket.py

@@ -60,18 +60,37 @@ class SocketAuthError(Exception):
     def __init__(self, msg):
         self.msg = msg
 
+class CloseErrorInfo(object):
+    def __init__(self, status_code, err_msg):
+        self.status_code = status_code
+        self.err_msg = err_msg
+
 class SocketConnection(sockjs.tornado.SockJSConnection):
     def on_open(self, info):
         log_data = dict(extra='[transport=%s]' % (self.session.transport_name,))
         record_request_start_data(log_data)
 
+        ioloop = tornado.ioloop.IOLoop.instance()
+
         self.authenticated = False
         self.session.user_profile = None
-        self.browser_session_id = info.get_cookie(settings.SESSION_COOKIE_NAME).value
-        self.csrf_token = info.get_cookie(settings.CSRF_COOKIE_NAME).value
+        self.close_info = None
+        try:
+            self.browser_session_id = info.get_cookie(settings.SESSION_COOKIE_NAME).value
+            self.csrf_token = info.get_cookie(settings.CSRF_COOKIE_NAME).value
+        except AttributeError:
+            # The request didn't contain the necessary cookie values.  We can't
+            # close immediately because sockjs-tornado doesn't expect a close
+            # inside on_open(), so do it on the next tick.
+            self.close_info = CloseErrorInfo(403, "Initial cookie lacked required values")
+            ioloop.add_callback(self.close)
+            return
 
-        ioloop = tornado.ioloop.IOLoop.instance()
-        self.timeout_handle = ioloop.add_timeout(time.time() + 10, self.close)
+        def auth_timeout():
+            self.close_info = CloseErrorInfo(408, "Timeout while waiting for authentication")
+            self.close()
+
+        self.timeout_handle = ioloop.add_timeout(time.time() + 10, auth_timeout)
         write_log_line(log_data, path='/socket/open', method='SOCKET',
                        remote_ip=info.ip, email='unknown', client_name='?')
 
@@ -173,11 +192,11 @@ class SocketConnection(sockjs.tornado.SockJSConnection):
     def on_close(self):
         log_data = dict(extra='[transport=%s]' % (self.session.transport_name,))
         record_request_start_data(log_data)
-        if self.session.user_profile is None:
+        if self.close_info is not None:
             write_log_line(log_data, path='/socket/close', method='SOCKET',
                            remote_ip=self.session.conn_info.ip, email='unknown',
-                           client_name='?', status_code=408,
-                           error_content='Timeout while waiting for authentication')
+                           client_name='?', status_code=self.close_info.status_code,
+                           error_content=self.close_info.err_msg)
         else:
             deregister_connection(self)
             write_log_line(log_data, path='/socket/close', method='SOCKET',