committing python app engine sample showing use of bigstore with service account
review details: http://codereview.appspot.com/5845055/
diff --git a/samples/storage_serviceaccount_appengine/app.yaml b/samples/storage_serviceaccount_appengine/app.yaml
new file mode 100644
index 0000000..88d00d5
--- /dev/null
+++ b/samples/storage_serviceaccount_appengine/app.yaml
@@ -0,0 +1,13 @@
+application: bucket-list-python 
+version: 1
+runtime: python27
+threadsafe: no
+api_version: 1
+
+handlers:
+- url: /listing.xsl
+  static_files: listing.xsl
+  upload: listing.xsl 
+
+- url: .*
+  script: main.py
diff --git a/samples/storage_serviceaccount_appengine/listing.xsl b/samples/storage_serviceaccount_appengine/listing.xsl
new file mode 100755
index 0000000..ba12ba4
--- /dev/null
+++ b/samples/storage_serviceaccount_appengine/listing.xsl
@@ -0,0 +1,32 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<xsl:stylesheet version="1.0" 
+  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+  xmlns:ama="http://doc.s3.amazonaws.com/2006-03-01">
+
+<xsl:template match="/">
+  <html>
+  <body>
+  <h2><a href="http://developer.google.com/storage">Google Cloud Storage</a> Content Listing for Bucket 
+      <xsl:value-of select="ama:ListBucketResult/ama:Name"/></h2>
+    <table border="1" cellpadding="5">
+      <tr bgcolor="#9acd32">
+        <th>Object Name</th>
+        <th>Modification Time</th>
+        <th>ETag</th>
+        <th>Size</th>
+        <th>Storage Class</th>
+      </tr>
+      <xsl:for-each select="ama:ListBucketResult/ama:Contents">
+      <tr>
+        <td><xsl:value-of select="ama:Key"/></td>
+        <td><xsl:value-of select="ama:LastModified"/></td>
+        <td><xsl:value-of select="ama:ETag"/></td>
+        <td><xsl:value-of select="ama:Size"/></td>
+        <td><xsl:value-of select="ama:StorageClass"/></td>
+      </tr>
+      </xsl:for-each>
+    </table>
+  </body>
+  </html>
+</xsl:template>
+</xsl:stylesheet>
diff --git a/samples/storage_serviceaccount_appengine/main.py b/samples/storage_serviceaccount_appengine/main.py
new file mode 100644
index 0000000..738a109
--- /dev/null
+++ b/samples/storage_serviceaccount_appengine/main.py
@@ -0,0 +1,97 @@
+#!/usr/bin/env python
+#
+# Copyright 2007 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+"""This application produces formatted listings for Google Cloud
+   Storage buckets.
+
+It takes a bucket name in the URL path and does an HTTP GET on the 
+corresponding Google Cloud Storage URL to obtain a listing of the 
+bucket contents. For example, if this app is invoked with the URI 
+http://bucket-list.appspot.com/foo, it would remove the bucket name 
+'foo', append it to the Google Cloud Storage service URI and send 
+a GET request to the resulting URI. The bucket listing is returned 
+in an XML document, which is prepended with a reference to an XSLT 
+style sheet for human readable presentation.
+
+More information about using Google App Engine apps and service accounts
+to call Google APIs can be found here:
+
+<https://developers.google.com/accounts/docs/OAuth2ServiceAccount>
+<http://code.google.com/appengine/docs/python/appidentity/overview.html>
+"""
+
+__author__ = 'marccohen@google.com (Marc Cohen)'
+
+import httplib2
+import logging
+import os
+import pickle
+import re
+
+from google.appengine.api import memcache
+from google.appengine.ext import webapp
+from google.appengine.ext.webapp import template
+from google.appengine.ext.webapp.util import run_wsgi_app
+from oauth2client.appengine import AppAssertionCredentials
+
+# Constants for the XSL stylesheet and the Google Cloud Storage URI.
+XSL = '\n<?xml-stylesheet href="/listing.xsl" type="text/xsl"?>\n';
+URI = 'http://commondatastorage.googleapis.com'
+
+# Obtain service account credentials and authorize HTTP connection.
+credentials = AppAssertionCredentials(
+    scope='https://www.googleapis.com/auth/devstorage.read_write')
+http = credentials.authorize(httplib2.Http(memcache))
+
+
+class MainHandler(webapp.RequestHandler):
+
+  def get(self):
+    try:
+      # Derive desired bucket name from path after domain name.
+      bucket = self.request.path
+      if bucket[-1] == '/':
+        # Trim final slash, if necessary.
+        bucket = bucket[:-1]
+      # Send HTTP request to Google Cloud Storage to obtain bucket listing.
+      resp, content = http.request(URI + bucket, "GET")
+      if resp.status != 200:
+        # If error getting bucket listing, raise exception.
+        err = 'Error: ' + str(resp.status) + ', bucket: ' + bucket + \
+              ', response: ' + str(content)
+        raise Exception(err)
+      # Edit returned bucket listing XML to insert a reference to our style 
+      # sheet for nice formatting and send results to client.
+      content = re.sub('(<ListBucketResult)', XSL + '\\1', content)
+      self.response.headers['Content-Type'] = 'text/xml'
+      self.response.out.write(content)
+    except Exception as e:
+      self.response.headers['Content-Type'] = 'text/plain'
+      self.response.set_status(404)
+      self.response.out.write(str(e))
+
+
+def main():
+  application = webapp.WSGIApplication(
+      [
+       ('.*', MainHandler),
+      ],
+      debug=True)
+  run_wsgi_app(application)
+
+
+if __name__ == '__main__':
+  main()