class ClienteForm(forms.ModelForm):

cnpj = forms.CharField(
    label = "CNPJ", widget=forms.TextInput(),
    required = True)

email = forms.EmailField(label='E-mail', required = True)

def clean_email(self):
    email = self.cleaned_data['email']
    if Cliente.objects.filter(email=email).exists():
        print("Email já existe")
        raise forms.ValidationError('Email ja cadastrado!')
    return email


def save(self, commit = True):
    user = super(ClienteForm,self).save(commit =False)
    user.set_password(self.cleaned_data['password1']) #Quem autentica é User!
    user.username = Cliente.objects.count() + Contador.objects.count() + 1
    if commit:
        user.save()
    return user

class Meta:
    model = Cliente
    fields =  ['razao_social','celular','cnpj','telefone','email']

<form class="pure-form pure-form-stacked" method="post">
          {% csrf_token %}
          {{ formCliente.non_field_errors }}

         <div class="field-wrap">
            <label>
            Razão Social<span class="req">*</span>
            </label>
            {{ formCliente.razao_social }}
            {{ formCliente.razao_social.errors }}
          </div>

          <div class="field-wrap">

            <label>
            CNPJ<span class="req">*</span>
            </label>
            {{ formCliente.cnpj }}
            {{ formCliente.cnpj.errors }}
          </div>

          <div class="field-wrap">
            <label>
            Email<span class="req">*</span>
            </label>
            {{ formCliente.email }}
            <div>{{ formCliente.email.errors }}</div>

          </div>


          <div class="field-wrap">
            <label>
            Telefone
            </label>
            {{ formCliente.telefone }}
            {{ formCliente.telefone.errors }}
          </div>

          <div class="field-wrap">
            <label>
            Celular
            </label>
            {{ formCliente.celular }}
            {{ formCliente.celular.errors }}
          </div>



          <div class="field-wrap">
            <label>
            Senha<span class="req">*</span>
            </label>
            {{ formCliente.password1 }}
            {{ formCliente.password1.errors }}
          </div>


          <div class="field-wrap">
            <label>
            Confirme a senha<span class="req">*</span>
            </label>
            {{ formCliente.password2 }}
            {{ formCliente.password2.errors }}
          </div>

          <p class="forgot"><a href="{% url 'accounts:page_login' %}">Acessar sua conta?</a></p>

          <button type="submit" class="button button-block"/>Cadastrar</button>


      </form>

def register(request):
template_name = 'register.html'
if request.method == 'POST':
    clienteForm = ClienteForm(request.POST)
    if clienteForm.is_valid():
        cliente = clienteForm.save()


formCliente = ClienteForm()

context = {
    'formCliente':formCliente
}

return render(request, template_name, context)

def register(request):
    template_name = 'register.html'
    if request.method == 'POST':
        form = ClienteForm(request.POST)
        if form.is_valid():
            form.save()
    else:
        form = ClienteForm()
    context = {
        'form': form
    }
    return render(request, template_name, context)