utils: allow to set an attribute on __init__ method to tell they need the request parameter

portail_citoyen/apps/passerelle_register_plugin/forms.py

@@ -38,6 +38,7 @@ class PasserelleRegisterForm(forms.Form):
                             choices=choices, initial=initial,
                             widget=widgets.CheckboxMultipleSelect,
                             required=False)
+    __init__.need_request = True
 
 
     def save(self):

portail_citoyen/utils.py

@@ -1,4 +1,6 @@
 def callable_has_arg(method, arg):
+    if hasattr(method, 'need_'+arg):
+        return getattr(method, 'need_'+arg)
     if hasattr(method, 'im_func'):
         varnames = method.im_func.func_code.co_varnames
         argcount = method.im_func.func_code.co_argcount