routing: do not catch TypeError too wildly

The current scope if try/except it way larger than it needs to be, which could
make it catch errors that are not tied to the method being called.

pecan/routing.py

@@ -173,15 +173,16 @@ def lookup_controller(obj, remainder, request=None):
 def handle_lookup_traversal(obj, args):
     try:
         result = obj(*args)
+    except TypeError as te:
+        logger.debug('Got exception calling lookup(): %s (%s)',
+                     te, te.args)
+    else:
         if result:
             prev_obj = obj
             obj, remainder = result
             # crossing controller boundary
             cross_boundary(prev_obj, obj)
             return result
-    except TypeError as te:
-        logger.debug('Got exception calling lookup(): %s (%s)',
-                     te, te.args)
 
 
 def find_object(obj, remainder, notfound_handlers, request):

pecan/tests/test_base.py

@@ -343,6 +343,17 @@ class TestLookups(PecanTestCase):
         r = app.get('/foo/bar', expect_errors=True)
         assert r.status_int == 404
 
+    def test_lookup_with_wrong_return(self):
+        class RootController(object):
+            @expose()
+            def _lookup(self, someID, *remainder):
+                return 1
+
+        app = TestApp(Pecan(RootController()))
+        self.assertRaises(TypeError,
+                          app.get,
+                          '/foo/bar', expect_errors=True)
+
 
 class TestCanonicalLookups(PecanTestCase):