Redis TypeError: must be string or buffer, not None

Question

I want to set a django model in my redis data store, and then in another view function, I want to get it and reuse it again; but it turns out to say:

TypeError: must be string or buffer, not None.

This is my code in views.py:

connection = redis.Redis('localhost')    
def recharge_account(request):

     cur = recharge_form.cleaned_data['currency']
                amnt = recharge_form.cleaned_data['amount']
                user_profile = models.UserProfile.objects.get(user=models.User.objects.get(id=request.user.id))
                user_b_account, created = models.BankAccount.objects.get_or_create(
                    owner=user_profile,
                    cur_code=cur,
                    method=models.BankAccount.DEBIT,
                    name=request.user.username + '_' + cur + '_InterPay-account',
                    account_id=make_id()
                )
                #  saving the temporarily deposit in redis
                deposit_dict = {"account": user_b_account, "amount": amnt, "banker": user_profile,
                                "date": user_b_account.when_opened, "cur_code": cur}
                pickled_deposit_dict = pickle.dumps(deposit_dict)
                cached_deposit_name = str(user_profile.user_id) + "-cachedDeposit"
                connection.set(cached_deposit_name, pickled_deposit_dict)

    ....    
       
    


 def callback_handler(request, amount):
    #getting from redis
                        new_deposit = pickle.loads(
                            connection.get(str(user_profile.user_id) + "-cachedDeposit")) 
                        deposit = models.Deposit(account=new_deposit['account'], amount=new_deposit['amount'],
                                                 banker=new_deposit['banker'],
                                                 date=new_deposit['date'], cur_code=new_deposit['cur_code'])
                        deposit.save()
                       .....

My question is: is there any problem with my procedure? Is there any problem with saving a django model in redis?

What should I do to get this function to work properly and getting the saved data "not to be None"?