Your view function is also called login, and the call to login(request, user) ends up being interpreted as a attempt to call this function recursively:
def login(request):
...
login(request, user)
To avoid it rename your view function or refer to the login from django.contrib.auth in some different way. You could for example change the import to rename the login function:
from django.contrib.auth import login as auth_login
...
auth_login(request, user)