Correctly handle noValueToken in RadioWidget

For a RadioWidget which is not required the the '--NOVALUE--' token is
not handled correctly. This will not be part of self.terms. Handle this
case separately.

CHANGES.txt

@@ -5,7 +5,7 @@ CHANGES
 3.2.2 (unreleased)
 ------------------
 
-- Nothing changed yet.
+- Correctly handle noValueToken in RadioWidget
 
 
 3.2.1 (2014-06-09)

src/z3c/form/browser/radio.py

@@ -22,6 +22,7 @@
 import zope.schema
 import zope.schema.interfaces
 from zope.i18n import translate
+from zope.schema.vocabulary import SimpleTerm
 from zope.pagetemplate.interfaces import IPageTemplate
 
 from z3c.form import interfaces, util
@@ -41,9 +42,17 @@ def isChecked(self, term):
         return term.token in self.value
 
     def renderForValue(self, value):
-        term = self.terms.getTermByToken(value)
+        terms = list(self.terms)
+        try:
+            term = self.terms.getTermByToken(value)
+        except LookupError:
+            if value == SequenceWidget.noValueToken:
+                term = SimpleTerm(value)
+                terms.insert(0, term)
+            else:
+                raise
         checked = self.isChecked(term)
-        id = '%s-%i' % (self.id, list(self.terms).index(term))
+        id = '%s-%i' % (self.id, terms.index(term))
         item = {'id': id, 'name': self.name, 'value': term.token,
                 'checked': checked}
         template = zope.component.getMultiAdapter(