Get all the subnets in a particular vpc tier

tier_subnetsV2.py

## Usage "{{ lookup('tier_subnets', 'vpc_id=vpc-7fb0841a tier=dmz1') }}"
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

import boto
import boto.vpc
import boto.ec2

from ansible.plugins.lookup import LookupBase
from ansible.errors import AnsibleError
from ansible.module_utils.ec2 import *

class LookupModule(LookupBase):

    def run(self, terms, variables=None, **kwargs):
        if isinstance(terms, basestring):
           terms = [ terms ]

        ret = []
        meta_params = dict(vpc_id=None, tier=None)

        try:
            vpc = boto.vpc.VPCConnection()
        except Exception, e:
            raise AnsibleError('Boto authentication issue: %s' % e)

        for term in terms:
            params = term.split()
            try:
                for param in params:
                    key, value = param.split('=') 
                    assert(key in meta_params)
                    if key == 'vpc_id':
                        meta_params['vpc_id'] = value 
                    if key == 'tier':
                        meta_params['tier'] = value
            except (ValueError, AssertionError) as e:
                raise AnsibleError(e)

        vpc_id=meta_params['vpc_id']
        tier=meta_params['tier']
        filter_params={
        'vpc_id': vpc_id,
        'tag:tier': tier
        }

        subnets_in_vpc = vpc.get_all_subnets(filters=filter_params)

        for subnet in subnets_in_vpc:
            ret.append(subnet.id) 

        return ret