Custom error messages and custom validation

Using Django
1

I read and understood in the documentation that it is possible to make custom validations for the model serializer class. However I don’t know how to catch the custom error message. I created the custom error messages and raise them in the validate_request() method in the UserPostSerializer class but the message I include doesn’t go to the serializer.errors in the view method for POST

This is what I’ve brewed up while testing this. It does raise the exception but it doesn’t give me the message which I included in the serializer class:

class UsersAPIview(APIView):
    def post(self, request):
        mydata = request.data
        serializer = UserPostSerializer(data=mydata)
        if serializer.is_valid():
            try:
                #Calling my custom validation method
                serializer.validate_request(mydata) #Should raise my custom ValidationError
            except ValidationError: 
                #serializer.errors only works after calling is_valid()
                return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST) 
                #I want to return my custom error message here but it's returning an empty dict {} instead.
                
            serializer.save()
            return Response(serializer.data, status=status.HTTP_201_CREATED)
    
        return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)

This is the serializer class for the view:

class UserPostSerializer(serializers.ModelSerializer):
    class Meta:
        model = Users
        fields = ['username', 'password']

    def validate_request(self, request_data):
        """This is my custom validation method"""
        #Validate attributes
        list_keys = request_data.keys()
        if len(list_keys)!=2:
            raise serializers.ValidationError({'Error':'Invalid attributes'})
        try:
            pw = request_data['password']
            usn = request_data['username']
        except:
            raise serializers.ValidationError({'Error':'Request must have password and username'})

        #Custom length validation for testing purposes
        if len(pw)<5 or len(usn)<5:
            raise serializers.ValidationError({'Error':'Pw and usn must have length <5'})

        return

UPDATE:
I’ve resorted to returning integers in the custom validation and storing a dict in the view to access custom errors.