The dhcpleases example had an old usage of print function. The formating
of leases record was also wrong.

The event-test example had an old usage of exceptions.

It's mainly to make examples compatible with python3.

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>

This API returns a list of DHCP leases for all network interfaces
connected to the given virtual network or limited output just for one
interface if mac is specified.

Example Output:
[{'iface': 'virbr3', 'ipaddr': '192.168.150.181', 'hostname': 'ubuntu14',
    'expirytime': 1403737495L, 'prefix': 24, 'clientid': None,
    'mac': '52:54:00:e8:73:eb', 'iaid': None, 'type': 0},
 {'iface': 'virbr3', 'ipaddr': '2001:db8:ca2:2:1::bd', 'hostname': 'fedora20-test',
    'expirytime': 1403738587L, 'prefix': 64, 'clientid': '00:04:b1:d8:86:42:e1:6a:aa:cf:d5:86:94:23:6f:94:04:cd',
    'mac': '52:54:00:5b:40:98', 'iaid': '5980312', 'type': 1}]

Signed-off-by: Peter Krempa <pkrempa@redhat.com>