Connecting to Google Cloud Storage using standalone Python script using service account

I am trying to connect to Google Cloud Storage from a standalone python script using a service account. I am running this script from my local system. I have also activated the service account using gcloud auth and added "GOOGLE_APPLICATION_CREDENTIALS" to point to the client_secrets.json file.

The authentication does not work and fails with the following log:

    Uploading object..
    Traceback (most recent call last):
      File "quickstart.py", line 122, in 
        main(args.bucket, args.filename, args.reader, args.owner)
      File "quickstart.py", line 16, in main
        resp = upload_object(bucket, filename, readers, owners)
      File "quickstart.py", line 43, in upload_object
        service = create_service()
      File "quickstart.py", line 39, in create_service
        return discovery.build('storage', 'v1', http=http_auth)
      File "build/bdist.macosx-10.12-intel/egg/oauth2client/util.py", line 137, in positional_wrapper
      File "build/bdist.macosx-10.12-intel/egg/googleapiclient/discovery.py", line 214, in build
      File "build/bdist.macosx-10.12-intel/egg/googleapiclient/discovery.py", line 261, in _retrieve_discovery_doc
      File "build/bdist.macosx-10.12-intel/egg/oauth2client/transport.py", line 153, in new_request
      File "build/bdist.macosx-10.12-intel/egg/oauth2client/client.py", line 765, in _refresh
      File "build/bdist.macosx-10.12-intel/egg/oauth2client/client.py", line 797, in _do_refresh_request
      File "/Library/Python/2.7/site-packages/httplib2-0.9.2-py2.7.egg/httplib2/__init__.py", line 1609, in request
        (response, content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
      File "/Library/Python/2.7/site-packages/httplib2-0.9.2-py2.7.egg/httplib2/__init__.py", line 1351, in _request
        (response, content) = self._conn_request(conn, request_uri, method, body, headers)
      File "/Library/Python/2.7/site-packages/httplib2-0.9.2-py2.7.egg/httplib2/__init__.py", line 1272, in _conn_request
        conn.connect()
      File "/Library/Python/2.7/site-packages/httplib2-0.9.2-py2.7.egg/httplib2/__init__.py", line 1036, in connect
        self.disable_ssl_certificate_validation, self.ca_certs)
      File "/Library/Python/2.7/site-packages/httplib2-0.9.2-py2.7.egg/httplib2/__init__.py", line 80, in _ssl_wrap_socket
        cert_reqs=cert_reqs, ca_certs=ca_certs)
      File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ssl.py", line 911, in wrap_socket
        ciphers=ciphers)
      File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/ssl.py", line 520, in __init__
        self._context.load_verify_locations(ca_certs)
    IOError: [Errno 13] Permission denied

Here is the code snipped I am trying to run to authenticate:

    import oauth2client
    from oauth2client.service_account import ServiceAccountCredentials
    from httplib2 import Http
    from googleapiclient import discovery
    import argparse
    import filecmp
    import json
    import tempfile
    import logging

    logging.basicConfig(filename='debug.log',level=logging.DEBUG)


    def main(bucket, filename, readers=[], owners=[]):
        print('Uploading object..')
        resp = upload_object(bucket, filename, readers, owners)
        print(json.dumps(resp, indent=2))


    def create_service():
        scopes = ['https://www.googleapis.com/auth/devstorage.read_write']
        credentials = ServiceAccountCredentials.from_json_keyfile_name('client_secrets.json', scopes)
        http_auth = credentials.authorize(Http())
        return discovery.build('storage', 'v1', http=http_auth)


    def upload_object(bucket, filename, readers, owners):
        service = create_service()

        # This is the request body as specified:
        # http://g.co/cloud/storage/docs/json_api/v1/objects/insert#request
        body = {
            'name': filename,
        }

        # If specified, create the access control objects and add them to the
        # request body
        if readers or owners:
            body['acl'] = []

        for r in readers:
            body['acl'].append({
                'entity': 'user-%s' % r,
                'role': 'READER',
                'email': r
            })
        for o in owners:
            body['acl'].append({
                'entity': 'user-%s' % o,
                'role': 'OWNER',
                'email': o
            })

        # Now insert them into the specified bucket as a media insertion.
        # http://g.co/dv/resources/api-libraries/documentation/storage/v1/python/latest/storage_v1.objects.html#insert
        with open(filename, 'rb') as f:
            req = service.objects().insert(
                bucket=bucket, body=body,
                # You can also just set media_body=filename, but for the sake of
                # demonstration, pass in the more generic file handle, which could
                # very well be a StringIO or similar.
                media_body=http.MediaIoBaseUpload(f, 'application/octet-stream'))
            resp = req.execute()

        return resp

I tried looking at multiple examples from google developers forum as well as other blogs. All show the same code. Not sure what is going wrong here.