Small speed-ups, avoid raising two exceptions during traversal.

This removes two exceptions and one import-lock from the normal
traversal logic used in the WSGI publisher.

src/OFS/Application.py

@@ -108,6 +108,11 @@ def Redirect(self, destination, URL1):
     ZopeRedirect = Redirect
 
     def __bobo_traverse__(self, REQUEST, name=None):
+        if name is None:
+            # Make this more explicit, otherwise getattr(self, name)
+            # would raise a TypeErorr getattr(): attribute name must be string
+            return None
+
         if name == 'Control_Panel':
             return APP_MANAGER.__of__(self)
         try:

src/OFS/ObjectManager.py

@@ -790,11 +790,8 @@ def __getitem__(self, key):
             method = request.get('REQUEST_METHOD', 'GET')
             if (request.maybe_webdav_client and
                     method not in ('GET', 'POST')):
-                try:
+                if bbb.HAS_ZSERVER:
                     from webdav.NullResource import NullResource
-                except ImportError:
-                    pass
-                else:
                     return NullResource(self, key, request).__of__(self)
         raise KeyError(key)
 

src/ZPublisher/BaseRequest.py

@@ -19,7 +19,6 @@
 from Acquisition import aq_base, aq_inner
 from Acquisition.interfaces import IAcquirer
 from ExtensionClass import Base
-import pkg_resources
 from six.moves.urllib.parse import quote as urllib_quote
 from zExceptions import Forbidden
 from zExceptions import NotFound
@@ -36,19 +35,15 @@
 from zope.traversing.namespace import namespaceLookup
 from zope.traversing.namespace import nsParse
 
+from App.bbb import HAS_ZSERVER
 from ZPublisher.Converters import type_converters
 from ZPublisher.interfaces import UseTraversalDefault
 
-HAS_ZSERVER = True
-try:
-    dist = pkg_resources.get_distribution('ZServer')
-except pkg_resources.DistributionNotFound:
-    HAS_ZSERVER = False
-
+if HAS_ZSERVER:
+    from ZServer.ZPublisher.xmlrpc import is_xmlrpc_response
+else:
     def is_xmlrpc_response(response):
         return False
-else:
-    from ZServer.ZPublisher.xmlrpc import is_xmlrpc_response
 
 _marker = []
 UNSPECIFIED_ROLES = ''
@@ -418,8 +413,11 @@ def traverse(self, path, response=None, validated_hook=None):
         # to possibly traverse to an alternate top-level object.
         if hasattr(object, '__bobo_traverse__'):
             try:
-                object = object.__bobo_traverse__(request)
-                self.roles = getRoles(None, None, object, UNSPECIFIED_ROLES)
+                new_object = object.__bobo_traverse__(request)
+                if new_object is not None:
+                    object = new_object
+                    self.roles = getRoles(None, None, object,
+                                          UNSPECIFIED_ROLES)
             except Exception:
                 pass
 
@@ -444,9 +442,9 @@ def traverse(self, path, response=None, validated_hook=None):
         self._post_traverse = post_traverse = []
 
         # import time ordering problem
-        try:
+        if HAS_ZSERVER:
             from webdav.NullResource import NullResource
-        except ImportError:
+        else:
             NullResource = None
 
         entry_name = ''