Switch Dockerfile from python:2.7-alpine to python:3.7-alpine (#1055)
Switch Dockerfile from python:2.7-alpine to python:3.7-alpine (#1055)


CTFd/CTFd,isislab/CTFd,ajvpot/CTFd,LosFuzzys/CTFd,isislab/CTFd,CTFd/CTFd,LosFuzzys/CTFd,LosFuzzys/CTFd,ajvpot/CTFd,isislab/CTFd,LosFuzzys/CTFd,CTFd/CTFd,ajvpot/CTFd,CTFd/CTFd,isislab/CTFd,ajvpot/CTFd