gw2api.v2.items.get_all() doesn't seem to produce a valid request.
requests.exceptions.HTTPError: 400 Client Error: unable to use 'all' keyword for this API for url: https://api.guildwars2.com/v2/items?lang=en&ids=all
From the GW2 API docs:
Request the list of all available items ids when the root endpoint (v2/items) has been accessed.
Should probably be: GET https://api.guildwars2.com/v2/items?lang=en