HACK: pypdf compatibility patch

We no longer use pypdf but use pypdf2, due to some bugs, we have some
pypdf objects in object database, so create a fake module so that we can
load them.

In a prefious version of this patch we have left some
Products.ERP5.NameObject in the database and saving new version of the
docuement (edit) fails with:
PicklingError: Can't pickle <class 'Products.ERP5.NameObject'>:
attribute lookup Products.ERP5.NameObject failed

product/ERP5/__init__.py

@@ -98,3 +98,19 @@ def initialize( context ):
 # backward compatibility names
 XML = None
 UI = None
+
+
+# pyPdf has been replaced by pyPdf2, but there was https://nexedi.erp5.net/bug_module/20141204-33F729
+try:
+  import pyPdf
+except ImportError:
+  class pyPdfGeneric:
+    class NameObject(str):
+      pass
+  # XXX Seems both generic and Generic existed.
+  sys.modules['pyPdf.Generic'] = pyPdfGeneric
+  sys.modules['pyPdf.generic'] = pyPdfGeneric
+  sys.modules['pyPdf'] = pyPdfGeneric
+
+# XXX previous version of this patch made that some documents have an instance of Products.ERP5.NameObject
+NameObject = pyPdfGeneric.NameObject