old_contents: from django.shortcuts import render, redirect
  from django.http import HttpResponse
  from django.core.urlresolvers import reverse
  from django.contrib.auth import login, authenticate
  from django.contrib import messages
  
  from users.models import User
  
  
  def join_us(request):
      
      # GET method 로 받았을 때
      if request.method == "GET":
          return render(
                  request,
                  'users/joinus.html',
                  context={}
                  )
  
      # POST method 로 받았을 때
      elif request.method == "POST":
          username = request.POST.get("username")
          checkpassword = request.POST.get("checkpassword")
          password = request.POST.get("password")
  
          clients_already_exist = User.objects.filter(username=username)
  
          # POST로 받은 username이 이미 존재하는 username일 경우
          if clients_already_exist:
              messages.add_message(
                      request,
                      messages.WARNING,
                      "중복된 아이디입니다."
                      )
              return redirect(reverse(join_us))
  
          # 패스워드와 패스워드 확인이 일치할 경우
          elif checkpassword == password:
              created_user = User.objects.create_user(
                      username=username,
                      password=password,
                      )
  
              created_user = authenticate(
                      username=username,
                      password=password,
                      )
  
              login(request, created_user)
  
              return redirect(reverse("aftersocial"))
  
          #일치하지 않을 경우
          return redirect(reverse("join_us"))
  
new_contents: from django.shortcuts import render, redirect
  from django.http import HttpResponse
  from django.core.urlresolvers import reverse
  from django.contrib.auth import login, authenticate
  from django.contrib import messages
  
  from users.models import User
  
  
  def join_us(request):
  
      # GET method 로 받았을 때
      if request.method == "GET":
          return render(
                  request,
                  'users/joinus.html',
                  context={}
                  )
  
      # POST method 로 받았을 때
      elif request.method == "POST":
          username = request.POST.get("username")
          checkpassword = request.POST.get("checkpassword")
          password = request.POST.get("password")
  
          clients_already_exist = User.objects.filter(username=username)
  
          # POST로 받은 username이 이미 존재하는 username일 경우
          if clients_already_exist:
              messages.add_message(
                      request,
                      messages.WARNING,
                      "중복된 아이디입니다."
                      )
              return redirect(reverse(join_us))
  
          # 패스워드와 패스워드 확인이 일치할 경우
          elif checkpassword == password:
              created_user = User.objects.create_user(
                      username=username,
                      password=password,
                      )
  
              created_user = authenticate(
                      username=username,
                      password=password,
                      )
  
              login(request, created_user)
  
              return redirect(reverse("aftersocial"))
  
          # 일치하지 않을 경우
          return redirect(reverse("join_us"))
  
subject: update : modify for pep8