Work around ZODB registering level names backwards.

Before Python 3.4, the logging module registered them in both
directions, but quit doing so in 3.4, breaking doctests which expected
to display custom level name ("BLATHER").

src/ZEO/tests/testZEO2.py

@@ -224,6 +224,13 @@ def some_basic_locking_tests():
     >>> logging.getLogger('ZEO').addHandler(handler)
     >>> logging.getLogger('ZEO').setLevel(logging.DEBUG)
 
+Work around the fact that ZODB registers level names backwards, which
+quit working in Python 3.4:
+
+    >>> import logging
+    >>> from ZODB.loglevels import BLATHER
+    >>> logging.addLevelName(BLATHER, "BLATHER")
+
 We start a transaction and vote, this leads to getting the lock.
 
     >>> zs1 = ZEO.tests.servertesting.client(server, '1')
@@ -435,6 +442,13 @@ Set up server and logging:
     >>> logging.getLogger('ZEO').addHandler(handler)
     >>> logging.getLogger('ZEO').setLevel(logging.DEBUG)
 
+Work around the fact that ZODB registers level names backwards, which
+quit working in Python 3.4:
+
+    >>> import logging
+    >>> from ZODB.loglevels import BLATHER
+    >>> logging.addLevelName(BLATHER, "BLATHER")
+
 Now, we'll start a transaction, get the lock and then mark the
 ZEOStorage as closed and see if trying to get a lock cleans it up: