python之'NoneType' 对象没有属性 'set_cookie'

我在 python 中获得了 Formwizard 的以下 django 代码。首先有两种形式:

 class AuthenticationForm(forms.Form): 
      FirstName = forms.CharField(max_length=500) 
      LastName = forms.CharField(max_length=500) 
 
 class SurveyForm(forms.Form): 
      def __init__(self, *args, **kwargs): 
       super(SurveyForm, self).__init__(*args, **kwargs) 
       for question in choiceValue: 
                self.fields[question] =  forms.ChoiceField(choices=CHOICES,widget=RadioSelect()) 
 
class ContactWizard(FormWizard): 
choiceValue = [] 
 
def get_template(self,step):  
    if step == 0: 
        return 'wizard0.html' 
    if step == 1: 
        return 'wizard1.html' 
 
def process_step(self, request, form, step): 
    if (step == 0):       
        fullName=""       
        if request.method== 'POST':                
            if form.is_valid():   
                FirstName = form.cleaned_data['FirstName'] 
                LastName = form.cleaned_data['LastName'] 
                FirstNameU=FirstName.capitalize() 
                LastNameU=LastName.capitalize() 
                fullName=FirstNameU+" "+LastNameU 
                personURIfn=GraphR.triples((None,FOAF_NS['givenName'],Literal(FirstNameU))) 
                personURIln=GraphR.triples((None,FOAF_NS['familyName'],Literal(LastNameU)))           
                for purifn in personURIfn: 
                    purifnStr='%s' %purifn[0] 
                    for puriln in personURIln:      
                        purilnStr='%s' %puriln[0] 
                        if purifnStr == purilnStr:                
                            personURI=purifnStr 
                            friendKnows=GraphR.triples((URIRef(purifnStr),FOAF_NS['knows'],None)) 
                            for fk in friendKnows: #and scn1 not in epuriList1:             
                                fkStr='%s' %fk[2] 
                                choiceValue.append(fkStr) 
                return render_to_response('wizard1.html', RequestContext(request)) 
 
 
def done(self, request, form_list): 
    print 'run' 

我不明白为什么它给出标题中提到的错误。此外，谷歌也不提供任何具体帮助。你们中的任何人都可以猜出它的原因。我怀疑 Done 方法中发生了错误，但不确定。

谢谢。

请您参考如下方法:

如果不是第 0 步，或者它是 GET 而不是 POST，或者表单无效，请考虑 process_step 中会发生什么。在这些情况下会返回什么？