got HttpError 404 for some times and get to work back !!

[Ahmad]

some times I get 

<HttpError 404 when requesting https://www.googleapis.com/calendar/v3/calendars/<email_address_here>?alt=json returned "Not Found">

then

I went to google calendar --for that email address-- and changed calendar settings to be public then it worked with no errors,

then I changed the settings back and deleted the calendar and imported it again with no errors.

this happened twice before and i don't know the reason,

I'm using google api python client

and here is my code if it can help:

_______________________________________________________

storage = Storage(CredentialsModel, 'id', request.user, 'credential')

    flow = OAuth2WebServerFlow(

            client_id='00000000.apps.googleusercontent.com',

            client_secret=aaaaaaaaQ__-aaaaaaaaae',

            scope='https://www.googleapis.com/auth/calendar',

            user_agent='appname/1.0',

            )

    credential = storage.get()

    if credential is None or credential.invalid == True:

        authorize_url = flow.step1_get_authorize_url(STEP2_URI)

        f = FlowModel(id=request.user, flow=flow)

        f.save()

        return HttpResponseRedirect(authorize_url)

    else:

        http = httplib2.Http()

        http = credential.authorize(http)

        service = build("calendar", "v3", http=http)

        calendar_id = request.user.email

        calendar = service.calendars().get(calendarId=calendar_id).execute()

________________________________________________________________

thanks in advance