Cannot connect to Skyscanner API using httplib2 in Python

Question

I'm trying to establish a connection via an http request to the Skyscanner API. I'm aware there is an ad hoc library in python to retrieve data from their API, but for learning purposes I want to create my own using httplib2.

I wrote the following code:

import sys
import httplib2
from urllib.parse import urlencode


class Connection(object):
    """Connect to Skyscanner Business API and retrieve quotes"""

    API_HOST = "http://partners.api.skyscanner.net"
    PRICING_SESSION_URL = "{api_host}/apiservices/pricing/v1.0".format(
        api_host=API_HOST)
    SESSION_HEADERS = {"Content-Type": "application/x-www-form-urlencode",
                       "Accept": "application/json"}

    def __init__(self, api_key="prtl6749387986743898559646983194", body=None):
        """
        :param api_key: the API key, the default is an API key provided for
        testing purposes in the Skyscanner API documentation
        :param body: the details of the flight we are interested on
        """

        if not api_key:
            raise ValueError("The API key must be provided")

        self.api_key = api_key
        self.body = body
        self.create_session(api_key=self.api_key, body=self.body)

    def get_result(self):
        pass

    def make_request(self, service_url, method="GET", headers=None, body=None):
        """Perform either a POST or GET request

        :param service_url: URL to request
        :param method: request method, default is GET
        :param headers: request headers
        :param data: the body of the request
        """

        if "apikey" not in service_url.lower():
            body.update({
                "apikey": self.api_key
            })

        h = httplib2.Http(".cache")
        response, content = h.request(service_url,
                                      method=method,
                                      body=urlencode(body),
                                      headers=headers)
        print(str(response))

    def create_session(self, api_key, body):
        """Create the Live Pricing Service session"""

        return self.make_request(self.PRICING_SESSION_URL,
                                 method="POST",
                                 headers=self.SESSION_HEADERS,
                                 body=body)

def main():
    body = {
        "country": "UK",
        "currency": "GBP",
        "locale": "en-GB",
        "originplace": "LOND-sky",
        "destinationplace": "NYCA-sky",
        "outbounddate": "2016-05-01",
        "inbounddate": "2016-05-10",
        "adults": 1
    }

    Connection(body=body)


if __name__ == "__main__":
    sys.exit(main())

What the code above does is to send a POST request to their API in order to create a Live Pricing session. To retrieve the data I should send a GET request with the URL to poll the booking details that would be specified in the Location header of the POST response.

The API key is publicly available on their documentation, as it's a generic one they suggest to use for experimenting with their API.

If I run the code above I get the following response:

{'content-length': '0', 'date': 'Sun, 24 Apr 2016 08:44:23 GMT', 'status': '415', 'cache-control': 'private'}

The documentation doesn't say what the Status 415 represents.