Only accept known locations in request.errors.add() (fixes #99)

cornice/errors.py

@@ -18,7 +18,7 @@ def add(self, location, name=None, description=None, **kw):
         """Registers a new error."""
         allowed = ('body', 'querystring', 'url', 'header', 'path',
                    'cookies', 'method')
-        if location not in allowed:
+        if location != '' and location not in allowed:
             raise ValueError('%r not in %s' % (location, allowed))
 
         self.append(dict(

cornice/tests/test_errors.py

@@ -7,6 +7,17 @@ class TestErrorsHelper(TestCase):
     def setUp(self):
         self.errors = Errors()
 
+    def test_add_to_supported_location(self):
+        self.errors.add('')
+        self.errors.add('body', description='!')
+        self.errors.add('querystring', name='field')
+        self.errors.add('url')
+        self.errors.add('header')
+        self.errors.add('path')
+        self.errors.add('cookies')
+        self.errors.add('method')
+        self.assertEqual(len(self.errors), 8)
+
     def test_raises_an_exception_when_location_is_unsupported(self):
         with self.assertRaises(ValueError):
             self.errors.add('something')