OAuth Gdata Python Client throws stacktrace on RSA_KEY

Moving on from AuthSub to OAuth, I think I'm slowly beginning to understand the process. This one threw me an error though:

#!/usr/bin/env python

from google.appengine.ext import webapp
from google.appengine.ext.webapp import util
from google.appengine.ext.webapp import template
from gdata.calendar import service
import gdata
from gdata.alt.appengine import run_on_appengine

from google.appengine.api import users
from google.appengine.ext import db

from gdata.auth import OAuthSignatureMethod, OAuthToken, OAuthInputParams
import urllib
import simplejson

import gdata.gauth

from google.appengine.runtime.apiproxy_errors import CapabilityDisabledError

SCOPES = 'https://www.google.com/calendar/feeds/' # in this case just one, but for future reference, just concatenate different scopes with a space in between
CONSUMER_KEY = 'jmm-timeline.appspot.com'
CONSUMER_SECRET = 'consumer secret key, here'
SIG_METHOD = gdata.auth.OAuthSignatureMethod.RSA_SHA1
f = open('remotekey.pem')
RSA_KEY = f.read()
f.close()


# Incomplete bibliography
# http://www.youtube.com/watch?v=bfgO-LXGpTM
# http://code.google.com/appengine/articles/python/retrieving_gdata_feeds.html


class BasePage(webapp.RequestHandler):
    title = "开发者_StackOverflowJoshua's Construction Zone"
    def write_page_header(self):
        self.response.out.write(template.render('templates/header.html', {'title': self.title}))

    def write_page_footer(self):
        self.response.out.write(template.render('templates/footer.html', {}))

class MainHandler(BasePage):
    def get(self):

        self.write_page_header()

        try:
            client = gdata.calendar.service.CalendarService(source='jmm-timeline-v1')
            run_on_appengine(client)
            client.SetOAuthInputParameters(gdata.auth.OAuthSignatureMethod.RSA_SHA1, consumer_key=CONSUMER_KEY, consumer_secret=CONSUMER_SECRET, rsa_key=RSA_KEY)
            req_token = client.FetchOAuthRequestToken(SCOPES)
            oauth_callback_url = 'http://jmm-timeline.appspot.com/handle_authorized_request_token'
            oauth_authorization_url = client.GenerateOAuthAuthorizationURL(callback_url=oauth_callback_url)
            self.response.out.write(template.render('templates/authorization_prompt.html', { 'authorization_url': oauth_authorization_url }))
        except CapabilityDisabledError, e:
            self.response.out.write(template.render('templates/content/maintenance.html'))

        self.write_page_footer()

class HandleAuthorizedRequestToken(BasePage):
    def get(self):
        self.write_page_header()

        client = gdata.calendar.service.CalendarService('jmm-timeline-2');
        run_on_appengine(client)


        self.write_page_footer()

def main():
    application = webapp.WSGIApplication([('/', MainHandler), ('/handle_authorized_request_token', HandleAuthorizedRequestToken)], debug=True)
    util.run_wsgi_app(application)


if __name__ == '__main__':
    main()

It appears as if gdata is trying to read my RSA_KEY string, and I get a stacktrace:

Traceback (most recent call last):
  File "C:\Program Files (x86)\Google\google_appengine\google\appengine\ext\webapp\__init__.py", line 515, in __call__
    handler.get(*groups)
  File "C:\Users\Joshua\appengineapps\jmm-timeline\main.py", line 52, in get
    req_token = client.FetchOAuthRequestToken(SCOPES)
  File "C:\Users\Joshua\appengineapps\jmm-timeline\gdata\service.py", line 415, in FetchOAuthRequestToken
    extra_parameters=extra_parameters)
  File "C:\Users\Joshua\appengineapps\jmm-timeline\gdata\auth.py", line 217, in GenerateOAuthRequestTokenUrl
    oauth_input_params.GetConsumer(), None)
  File "C:\Users\Joshua\appengineapps\jmm-timeline\gdata\oauth\__init__.py", line 171, in sign_request
    self.set_parameter('oauth_signature', self.build_signature(signature_method, consumer, token))
  File "C:\Users\Joshua\appengineapps\jmm-timeline\gdata\oauth\__init__.py", line 175, in build_signature
    return signature_method.build_signature(self, consumer, token)
  File "C:\Users\Joshua\appengineapps\jmm-timeline\gdata\oauth\rsa.py", line 55, in build_signature
    privatekey = keyfactory.parsePrivateKey(cert)
  File "C:\Users\Joshua\appengineapps\jmm-timeline\gdata\tlslite\utils\keyfactory.py", line 203, in parsePrivateKey
    return parseXMLKey(s, private=True)
  File "C:\Users\Joshua\appengineapps\jmm-timeline\gdata\tlslite\utils\keyfactory.py", line 79, in parseXMLKey
    key = Python_RSAKey.parseXML(s)
  File "C:\Users\Joshua\appengineapps\jmm-timeline\gdata\tlslite\utils\Python_RSAKey.py", line 137, in parseXML
    element = xmltools.parseAndStripWhitespace(s)
  File "C:\Users\Joshua\appengineapps\jmm-timeline\gdata\tlslite\utils\xmltools.py", line 30, in parseAndStripWhitespace
    raise SyntaxError(str(e))
SyntaxError: syntax error: line 1, column 0

---

tlslite has two keyformats: PEM and XML. It first tries PEM (see parsePrivateKey), and then falls back to XML. Apparently, there is an error in your PEM file, so PEM parsing fails (but should have succeeded). Parsing XML then clearly must fail.

My guess is that you messed up line endings somehow, but perhaps there is something even more fundamentally wrong with the PEM file.