boto3 Lacks EC2 Instance Identity Metadata Parsing

desc.md

Given that boto/boto3#313 is not resolved, I hacked together something else in Python that I'm using.

test.py

"""
NOTE: This unit test is ONLY good for python 3
"""
import mock
import unittest


class EC2Metadata(unittest.TestCase):
    class MockResponse(object):
        def __init__(self, resp_data=None, code=200, msg='OK'):
            if not resp_data:
                resp_data = """{
                    "devpayProductCodes" : null,
                    "availabilityZone" : "us-east-1d",
                    "privateIp" : "10.158.112.84",
                    "version" : "2010-08-31",
                    "region" : "us-east-1",
                    "instanceId" : "i-1234567890abcdef0",
                    "billingProducts" : null,
                    "instanceType" : "t1.micro",
                    "accountId" : "123456789012",
                    "pendingTime" : "2015-11-19T16:32:11Z",
                    "imageId" : "ami-5fb8c835",
                    "kernelId" : "aki-919dcaf8",
                    "ramdiskId" : null,
                    "architecture" : "x86_64"
                }"""

            self.resp_data = resp_data
            self.code = code
            self.msg = msg
            self.headers = {}

        def read(self):
            return self.resp_data

    @mock.patch('urllib.request.urlopen')
    def test_parse_ec2_instance_region(self, urlopen):
        """
        Check parsing of EC2 instance identity to determine region
        
        TODO: Make test py2 compatible
        """
        urlopen.return_value = self.MockResponse()

        from util import EC2InstanceIdentity
        instance_id = EC2InstanceIdentity()
        self.assertEqual(instance_id.region, 'us-east-1')

util.py

import json
try:
    #py3
    from urllib.request import urlopen

except ImportError:
    #py2
    from urllib2 import urlopen

class EC2InstanceIdentity(object):
    """
    Assists in discovery EC2 instance identity info
    Ref: http://docs.aws.amazon.com/AWSEC2/latest/WindowsGuide/instance-identity-documents.html
    """

    METADATA_URL = 'http://169.254.169.254/latest/dynamic/instance-identity/document'
    """What URL to hit for the instance identity document"""

    def __init__(self):
        self._json_document = None

    def __fetch_document(self):
        """
        Fetches the instance identity document & parses it
        """
        raw_document = urlopen(self.METADATA_URL).read()
        self._json_document = json.loads(raw_document)

    def __getattr__(self, attr_name):
        if not self._json_document:
            self.__fetch_document()

        return self._json_document[attr_name]