Code review comment for lp:~xianghui/charm-helpers/support-ipv6

Hui, I'm getting some lint errors:

$ make lint
Checking for Python syntax...
charmhelpers/contrib/hahelpers/cluster.py:183:25: F821 undefined name 'get_ipv6_addr'
charmhelpers/cli/commands.py:1:1: F401 'CommandLine' imported but unused
charmhelpers/cli/commands.py:2:1: F401 'host' imported but unused
tests/contrib/network/test_ip.py:161:78: W291 trailing whitespace
make: *** [lint] Error 1

Also, could you please update/add unit tests to cover the change you are making.