[BUG] Timezone bug in generate_jwt_token

[scaine1]

ALL software version info (bokeh, python, notebook, OS, browser, any other relevant packages)

bokeh: 2.0.1-42-g47e7da4b7
python: 3.8.2
OS: Mac OS X 10.15.3

Description of expected behavior and the observed behavior

see https://discourse.bokeh.org/t/timezone-bug-in-generate-jwt-token/5206

Stack traceback and/or browser JavaScript console output

On the django server we get

  File "/Users/simon/anaconda3/envs/owsforecasts/lib/python3.7/site-packages/bokeh/client/session.py", line 119, in pull_session
    session.pull()
  File "/Users/simon/anaconda3/envs/owsforecasts/lib/python3.7/site-packages/bokeh/client/session.py", line 348, in pull
    raise IOError("Cannot pull session document because we failed to connect to the server (to start the server, try the 'bokeh serve' command)")
OSError: Cannot pull session document because we failed to connect to the server (to start the server, try the 'bokeh serve' command)

From the Django app we get

Traceback (most recent call last):
  File "/Users/simon/anaconda3/lib/python3.6/site-packages/tornado/websocket.py", line 956, in _accept_connection
    open_result = handler.open(*handler.open_args, **handler.open_kwargs)
  File "/Users/simon/anaconda3/lib/python3.6/site-packages/bokeh/server/views/ws.py", line 135, in open
    raise ProtocolError("Token is expired.")
bokeh.protocol.exceptions.ProtocolError: Token is expired

Screenshots or screencasts of the bug in action