- add Zope 4 migration page for moved packages

docs/zope4/migration/index.rst

@@ -3,5 +3,6 @@ Migrating to Zope 4
 
 .. toctree::
 
+   removed
    zmi
    zodb

docs/zope4/migration/removed.rst

@@ -0,0 +1,51 @@
+Zope products that are now distributed separately
+=================================================
+During the Zope 4 development, several packages that used to be included
+have been separated out and ship separately.
+
+On this page the term "add to your application buildout" is used generically.
+How you do so depends on your chosen installation method, like adding an egg
+name to a `requirements file` for ``pip`` installs, or adding it to an ``eggs``
+specification for ``zc.buildout``.
+
+
+ZServer
+-------
+ZServer does not support Python 3. The following only applies for Zope 4 under
+Python 2.
+
+If you want to continue using ZServer instead of moving to WSGI you need to add
+the ZServer egg to your application buildout.
+
+If you use the recipe ``plone.recipe.zope2instance`` in a buildout, add it to
+its ``eggs`` attribute and also add the flag ``wsgi = off``.
+
+
+Sessioning
+----------
+If you have used (or want to use) the built-in support for sessioning, add the
+egg ``Products.Sessions`` to your application buildout.
+
+You also need to make sure that your Zope configuration file contains a ZODB
+configuration for a temporary folder like this::
+
+  <zodb_db temporary>
+      <temporarystorage>
+        name Temporary database (for sessions)
+      </temporarystorage>
+      mount-point /temp_folder
+      container-class Products.TemporaryFolder.TemporaryContainer
+  </zodb_db>
+
+
+External Methods
+----------------
+If you have External Method objects in your ZODB, make sure to add the egg
+``Products.ExternalMethod`` to your application buildout.
+
+
+Site Error Log
+--------------
+If you have used the Site Error Log (the ``error_logs`` objects that show
+information about errors occurring in your application), add the egg
+``Products.SiteErrorLog`` to your application buildout.