add support for file uploads to ckans < 2.2

[wardi]

Example client code:
https://github.com/OCHA-DAP/dap-scrapers/blob/master/ckan/endtoend.py

"""
curl $CKAN_INSTANCE/api/storage/auth/form/$DIRECTORY/$FILENAME -H Authorization:$CKAN_APIKEY > phase1
curl $CKAN_INSTANCE/storage/upload_handle -H Authorization:$CKAN_APIKEY --form file=@$FILENAME --form "key=$DIRECTORY/$FILENAME" > phase2
curl http://ckan.megginson.com/api/3/action/resource_create --data '{"package_id":"51b25ca0-9c2e-4e66-85e3-37a13c19a85d", "url":"'$CKAN_INSTANCE'/storage/f/'$DIRECTORY'/'$FILENAME'"}' -H Authorization:$CKAN_APIKEY > phase3
"""

import sys
import os
import requests
import datetime
import lxml.html
import json

def do(f, args=[], kwargs={}):
    while True:
        try:
            x=f(*args, **kwargs)
            return x
        except Exception, e:
            print "EXCEPTION: ",e
            pass

def raise_for_status(response):
    try:
        response.raise_for_status()
    except:
        print "FAILED RFS: %r" % response.content
        raise

def get_parameters(filepath=None):
    params = {}
    params['CKAN_INSTANCE'] = os.getenv("CKAN_INSTANCE")
    params['CKAN_APIKEY'] = os.getenv("CKAN_APIKEY")
    if not params['CKAN_INSTANCE'] or not params['CKAN_APIKEY']:
        raise RuntimeError("Enviroment variables CKAN_INSTANCE / CKAN_APIKEY not set.")

    if filepath is None:
        if len(sys.argv) != 2:
            raise RuntimeError("Takes one argument: filename")
        else:
            filepath = sys.argv[1]
    params['FILEPATH'] = filepath
    params['FILENAME'] = os.path.basename(params['FILEPATH'])

    params['NOW'] = datetime.datetime.now().isoformat()
    params['DIRECTORY'] = params['NOW'].replace(":", "").replace("-", "")
    return params

def request_permission():  # phase1
    response = requests.get("{CKAN_INSTANCE}/api/storage/auth/form/{DIRECTORY}/{FILENAME}".format(**params), headers=headers)
    response.raise_for_status()
    j = response.json()
    assert "action" in j
    assert "fields" in j
    print j
    return j

def upload_file(permission):  # phase 2
    response = requests.post("{CKAN_INSTANCE}{action}".format(action=permission['action'], **params),
                             headers=headers,
                             files={'file': (params['FILENAME'], open(params['FILEPATH']))},
                             data={permission['fields'][0]['name']: permission['fields'][0]['value']}
                             )
    response.raise_for_status()
    root = lxml.html.fromstring(response.content)
    h1, = root.xpath("//h1/text()")
    assert " Successful" in h1
    url, = root.xpath("//h1/following::a[1]/@href")
    assert params['FILENAME'] in url  # might be issues with URLencoding
    return url

def create_resource(url, **kwargs):  # phase 3
    data = {"url": url,
            "package_id": "51b25ca0-9c2e-4e66-85e3-37a13c19a85d"}
    newheader = dict(headers)
    newheader['Content-Type'] = "application/x-www-form-urlencoded"  # http://trac.ckan.org/ticket/2942
    data.update(kwargs)
    print data
    response = requests.post("{CKAN_INSTANCE}/api/3/action/resource_create".format(**params),
    # response = requests.post("http://httpbin.org/post".format(**params),
                             headers=newheader,
                             data=json.dumps(data)
                             )
    #response.raise_for_status()
    try:
        assert response.json()["success"]
    except:
        print "FAILED: %r" % response.content
        raise
    print response.content


def upload(resource_info=None, filename=None):
    global params
    global headers
    params = get_parameters(filename)
    headers = {"Authorization": params['CKAN_APIKEY']}
    if resource_info is None:
        print "No resource_info specified, using defaults"
        resource_info = {
            "package_id": "51b25ca0-9c2e-4e66-85e3-37a13c19a85d",
            "revision_id": params['NOW'],
            "description": "Indicators scraped from a variety of sources by ScraperWiki",
            "format": "Zipped CSV",
            # "hash": None,
            "name": "scraped.csv.zip",
            # "resource_type": None,
            "mimetype": "application/zip",
            "mimetype_inner": "text/csv",
            # "webstore_url": None,
            # "cache_url": None,
            # "size": None,
            "created": params['NOW'],
            "last_modified": params['NOW'],
            # "cache_last_updated": None,
            # "webstore_last_updated": None,
            }
    j = do(request_permission)
    url = do(upload_file, [j])
    do(create_resource, [url], resource_info)

if __name__=="__main__": upload()