What is the correct way to implement Django password history?

Question

I have implemented a solution for checking a new password against the last 5 passwords like so:

1. Created 5 fields in a user profile table to store the encrypted passwords
2. On creating a new user, I stored the initial password in encrypted form in all the 5 fields
3. On reset, I changed the views.py from Lib>django>contrib>auth directory from my virtual environment like so:

def form_valid(self, form):
    #all initial code to get the keys etc goes here

    newpwd = form.cleaned_data['new_password2']

    #get the unencrypted passwords from history
    p1 = cipher.decrypt(b64decode(user.pwd1))
    p2 = cipher.decrypt(b64decode(user.pwd2))
    p3 = cipher.decrypt(b64decode(user.pwd3))
    p4 = cipher.decrypt(b64decode(user.pwd4))
    p5 = cipher.decrypt(b64decode(user.pwd5))

    #check if the password is already used and redirect with error message
    if newpwd == p1 or newpwd == p2 or newpwd == p3 or newpwd == p4 or newpwd == p5:
        messages.error(self.request, _('New Password should be different from old password'))
        return redirect('password_change')
    else:
        #store the password in the password history
        user.pwd5=user.pwd4
        user.pwd4=user.pwd3
        user.pwd3=user.pwd2
        user.pwd2=user.pwd1
        user.pwd1=newpwd 
        user.save()
        form.save()
        messages.error(self.request,'Password Changed Successfully')
        return redirect('/user/login')

    form.save()
    # Updating the password logs out all other sessions for the user
    # except the current one.
    update_session_auth_hash(self.request, form.user)
    return super().form_valid(form)

This works fine. But it feels incorrect editing the existing contrib>auth files like this. Is there a way to implement the password history checking without changing the in built auth files?