Exception: bus.Bus unavailable

Traceback (most recent call last):
File "/odoo/odoo-server/odoo/http.py", line 650, in _handle_exception
  return super(JsonRequest, self)._handle_exception(exception)
File "/odoo/odoo-server/odoo/http.py", line 310, in _handle_exception
  raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
File "/odoo/odoo-server/odoo/tools/pycompat.py", line 87, in reraise
  raise value
File "/odoo/odoo-server/odoo/http.py", line 692, in dispatch
  result = self._call_function(**self.params)
File "/odoo/odoo-server/odoo/http.py", line 342, in _call_function
  return checked_call(self.db, *args, **kwargs)
File "/odoo/odoo-server/odoo/service/model.py", line 97, in wrapper
  return f(dbname, *args, **kwargs)
File "/odoo/odoo-server/odoo/http.py", line 335, in checked_call
  result = self.endpoint(*a, **kw)
File "/odoo/odoo-server/odoo/http.py", line 936, in __call__
  return self.method(*args, **kw)
File "/odoo/odoo-server/odoo/http.py", line 515, in response_wrap
  response = f(*args, **kw)
File "/odoo/odoo-server/addons/bus/controllers/main.py", line 37, in poll
  raise Exception("bus.Bus unavailable")
Exception: bus.Bus unavailable

Error above means you haven’t configured longpolling properly. Longpolling is used for instant notifications and updates. If you are sure that you don’t need it, you can ignore the error.

To fix the error check following page: How to enable Longpolling in odoo