More on MakeZopeAppSmaller:

* Move UserError to zope.exceptions. (While at it, restructure zope.exceptions
  a little bit).

browser/configure.zcml

@@ -0,0 +1,46 @@
+<zope:configure
+   xmlns:zope="http://namespaces.zope.org/zope"
+   xmlns="http://namespaces.zope.org/browser">
+
+  <page
+      for="zope.interface.common.interfaces.IException"
+      name="index.html"
+      template="systemerror.pt"
+      class="..systemerror.SystemErrorView"
+      permission="zope.Public"
+      />
+
+  <page
+      for="zope.exceptions.INotFoundError"
+      name="index.html"
+      template="systemerror.pt"
+      class="..systemerror.SystemErrorView"
+      permission="zope.Public"
+      />
+
+  <page
+      for="zope.security.interfaces.IUnauthorized"
+      name="index.html"
+      permission="zope.Public"
+      class=".unauthorized.Unauthorized"
+      />
+
+  <zope:adapter factory=".unauthorized.default_template" name="default" />
+
+  <page
+      for="zope.exceptions.interfaces.IUserError"
+      name="index.html"
+      permission="zope.Public"
+      template="user.pt"
+      class=".user.UserErrorView"
+      />
+
+  <page
+      for="zope.publisher.interfaces.INotFound"
+      name="index.html"
+      permission="zope.Public"
+      template="notfound.pt"
+      class=".notfound.NotFound"
+      />
+
+</zope:configure>

interfaces.py

@@ -0,0 +1,40 @@
+##############################################################################
+# Copyright (c) 2003 Zope Corporation and Contributors.
+# All Rights Reserved.
+# 
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+##############################################################################
+"""General exceptions
+
+$Id$
+"""
+__docformat__ = 'restructuredtext'
+
+from zope.interface import Interface, implements
+
+##############################################################################
+# BBB 2006/04/03 - to be removed after 12 months
+
+import zope.deferredimport
+zope.deferredimport.deprecated(
+    "UserError has been moved to zope.exceptions.interfaces. This "
+    "reference will be removed in Zope 3.5.",
+    UserError = 'zope.exceptions.interfaces:UserError',
+    IUserError = 'zope.exceptions.interfaces:IUserError',
+    )
+
+#
+##############################################################################
+
+class ISystemErrorView(Interface):
+    """Error views that can classify their contexts as system errors
+    """
+
+    def isSystemError():
+        """Return a boolean indicating whether the error is a system errror
+        """