Do you have create the SingUpForm. If you use Django auth model, can you create the forms.py file and import this path:
from django.contrib.auth.forms import UserCreationForm
from django.contrib.auth.models import User
inside of the forms.py file create the SingUpForm class and extends of the UserCreationForm module, example:
class SignUpForm(UserCreationForm):
class Meta:
model = User
fields = ('username', 'first_name', 'last_name', 'email', 'password1', 'password2', )
Before, in your sign_up view, import you SingUpForm.