Return snmp value for the next OID.

def get_next(self,oid):
		"""Return snmp value for the next OID."""
		try: # Nested try..except because of Python 2.4
			self.lock.acquire()
			try:
				# remove trailing zeroes from the oid
				while len(oid) > 0 and oid[-2:] == ".0" and oid not in self.data:
					oid = oid[:-2];
				return self.get(self.data_idx[self.data_idx.index(oid)+1])
			except ValueError:
				# Not found: try to match partial oid
				for real_oid in self.data_idx:
					if real_oid.startswith(oid):
						return self.get(real_oid)
				return "NONE" # Unknown OID
			except IndexError:
				return "NONE" # End of MIB
		finally:
			self.lock.release()