django即使密码错误也不发送邮件其显示的电子邮件已发送

from django.contrib.auth.backends import ModelBackend
from django.contrib.auth import get_user_model
from django.core.mail import send_mail

UserModel = get_user_model()

class CustomAuthBackend(ModelBackend):
    def authenticate(self, request, username=None, password=None, **kwargs):
        try:
            user = UserModel.objects.get(username=username)
            if user.check_password(password):
                return user
            else:
                # 发送电子邮件
                send_mail(
                    '密码错误',
                    '您的登录密码错误，请注意账户安全。',
                    'noreply@example.com',
                    [user.email],
                    fail_silently=True,
                )
        except UserModel.DoesNotExist:
            pass

    def get_user(self, user_id):
        try:
            return UserModel.objects.get(pk=user_id)
        except UserModel.DoesNotExist:
            return None

AUTHENTICATION_BACKENDS = [
    'myapp.backends.CustomAuthBackend',
    'django.contrib.auth.backends.ModelBackend',
]