String representation of a pymongo Connection instance is broken when only one host is specified and slave_okay is set to True. This was caused by commit c5e78293d5b3a758a9d2. The problem is that self._host and self._post aren't being set since we are skipping __try_node. This doesn't seem to affect connectivity since __connect will call __find_master directly if either of these attributes are set to None. The bug is mostly cosmetic.

repro:

Python 2.7.1 (r271:86832, Jan 19 2011, 14:07:10)
[GCC 4.4.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pymongo
>>> conn = pymongo.Connection('localhost', slave_okay=True)
>>> conn
Connection(None, None)
>>> conn.host
>>> repr(conn.host)
'None'
>>> repr(conn.port)
'None'
>>> conn = pymongo.Connection()
>>> conn
Connection(['localhost:27017', u'behackett-dt:27019', u'behackett-dt:27017', u'behackett-dt:27018'])