add lxml to base requirements
add lxml to base requirements

andylolz/UK-Polling-Stations,DemocracyClub/UK-Polling-Stations,chris48s/UK-Polling-Stations,DemocracyClub/UK-Polling-Stations,chris48s/UK-Polling-Stations,andylolz/UK-Polling-Stations,DemocracyClub/UK-Polling-Stations,chris48s/UK-Polling-Stations,andylolz/UK-Polling-Stations