ИМ
А как вы тогда во время тестов пароль для тестового юзера пишете?
student_user = User.objects.create_user(username=username,
first_name=first_name_student,
last_name=last_name_student,
email=email_student)
student_user.set_password(password)
student_user.save()
first_name=first_name_student,
last_name=last_name_student,
email=email_student)
student_user.set_password(password)
student_user.save()