ValidationError（”A”）のAが表示できない

前提・実現したいこと

パスワードが確認用パスワードと一致しない場合にフォームの上または下に”一致しません”と表示したい

該当のソースコード

form
1class RegisterForm(forms.ModelForm):
2    class Meta:
3        model = CostomUser
4        fields = ('username','last_name','first_name','password',)
5        widget = {
6        'password': forms.PasswordInput(attrs = {'placeholder':'password'}),
7        }
8    password2 = forms.CharField(
9        label = '確認用password',
10        required = True,
11        strip=False,
12        widget=forms.PasswordInput(attrs={'placeholder':'確認用password'})
13    )
14
15    def __init__(self,*args,**kwargs):
16        super().__init__(*args,**kwargs)
17        self.fields['username'].widget.attrs = {'placeholder':'username'}
18        for field in self.fields:
19            self.fields[field].required = True
20
21    def clean(self):
22        super().clean()
23        password = self.cleaned_data['password']
24        password2 = self.cleaned_data['password2']
25        if password != password2:
26            raise forms.ValidationError("パスワードと確認用パスワードが一致しません")
27        return password2
28

↑このValidationErrorはどういう働きをするのかがわかりません

view
1class RegisterView(FormView):
2
3    def get(self,request,*args,**kwargs):
4
5        return render(request,'schedule/signup.html',{'form':RegisterForm})
6
7    def post(self,request,*args,**kwargs):
8        form = RegisterForm(request.POST)
9        if form.is_valid():
10            user = form.save(commit=False)
11            user.set_password(form.cleaned_data['password'])
12            user.save()
13            return render(request,'schedule/register.html',{'form':form})
14
15
16
17
18signup = RegisterView.as_view()
19
20

html
1<!DOCTYPE html>
2<html>
3  <meta charset="utf-8">
4  <body>
5
6    <form action= "{% url 'schedule:signup' %}" method="post">
7        {{ form.errors.password }}
8        <label>{{ form.username.label }}{{ form.username}}</label><br/>
9        <label>{{ form.last_name.label }}{{ form.last_name}}</label><br/>
10        <label>{{ form.first_name.label }}{{ form.first_name}}</label><br/>
11        <label>{{ form.password.label }}{{ form.password}}</label><br/>
12        <label>{{ form.password2.label }}{{ form.password2}}</label><br/>
13        {% csrf_token %}
14        <input type="submit" value="登録">
15    </form>
16  </body>
17</html>
18