fix tests and improve changelog

CHANGES.rst

@@ -5,8 +5,8 @@
 4.0.0.dev (unreleased)
 ======================
 
-- improve logging when blob is not found: include the filename requested
-  which doesn't exists
+- Include the filename in the exception message to support debugging in case 
+  loadBlob does not find the file.
 
 4.0.0a4 (2012-12-17)
 =====================
@@ -315,7 +315,7 @@ Bugs fixed
   their subconnections weren't cleaned up properly.
 
 - ZEO didn't work with IPv6 addrsses.
-  Added IPv6 support contributed by Martin v. Löwis.
+  Added IPv6 support contributed by Martin v. L�wis.
 
 - A file storage bug could cause ZEO clients to have incorrect
   information about current object revisions after reconnecting to a

src/ZODB/tests/blob_transaction.txt

@@ -394,7 +394,7 @@ And we shouldn't be able to read the data that we saved:
     >>> blob_storage.loadBlob(blob._p_oid, s1)
     Traceback (most recent call last):
     ...
-    POSKeyError: 'No blob file'
+    POSKeyError: 'No blob file at ...'
 
 Of course the old data should be unaffected:
 
@@ -411,7 +411,7 @@ Similarly, the new object wasn't added to the storage:
     >>> blob_storage.loadBlob(blob._p_oid, s2)
     Traceback (most recent call last):
     ...
-    POSKeyError: 'No blob file'
+    POSKeyError: 'No blob file at ...'
 
 .. clean up