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In (at least) Python 2.5.2, logging.logRecord provides a very useful
facility to interpolate formatted strings. This feature expands an *args
sequence; if that sequence has only one element and that element is a
dictionary, LogRecord uses the dictionary to interpolate keyword
formatted strings. This is incredibly useful, but the LogRecord
__init__() method includes a rather arbitrary type-specific check that
prevents users from passing dict-like objects to the log methods:
logging.__init__.py:204..238
class LogRecord:
 [...]
 def __init__(self, name, level, pathname, lineno,
 msg, args, exc_info, func=None):
 [...]
 if args and (len(args) == 1) and args[0] and (type(args[0]) ==
types.DictType):
 args = args[0]
This restriction prevents the user from passing eg a subclass of
UserDict.DictMixin. Now, __init__() clearly does need to do _some_
checking of args, but it would be nice if that checking accepted
dict-like objects. I haven't come up with a good way to do this myself
yet, but I figured I'd submit the request now.
Thanks!

You don't need to change the logging package for this. Simply generate a
bona-fide dict from your UserDict or DictMixin subclass as follows:
dict(userDict_or_mixIn_instance)
and pass that into the logging call instead of userDict_or_mixIn_instance.