I can't use the download reports feature with the Python client. I'm using with adwords-15.9.0 with v201306. It always fails with: 

```
$ ./classifications.py 
Traceback (most recent call last):
  File "./classifications.py", line 48, in <module>
    download_report(client, client_id)
  File "./classifications.py", line 32, in download_report
    file_path = report_downloader.DownloadReportWithAwql(report_query, 'CSV', file_path=path)
  File "/Users/mike/.virtualenvs/xxx/lib/python2.7/site-packages/adspygoogle/adwords/ReportDownloader.py", line 127, in DownloadReportWithAwql
    fileobj) or file_path
  File "/Users/mike/.virtualenvs/xxx/lib/python2.7/site-packages/adspygoogle/adwords/ReportDownloader.py", line 169, in __DownloadAdHocReportWithAwql
    return self.__DownloadReport(payload, return_micros, fileobj)
  File "/Users/mike/.virtualenvs/xxx/lib/python2.7/site-packages/adspygoogle/adwords/ReportDownloader.py", line 184, in __DownloadReport
    headers = self.__GenerateHeaders(return_micros)
  File "/Users/mike/.virtualenvs/xxx/lib/python2.7/site-packages/adspygoogle/adwords/ReportDownloader.py", line 282, in __GenerateHeaders
    self._headers['oauth2credentials'].apply(headers)
  File "/Users/mike/.virtualenvs/xxx/lib/python2.7/site-packages/oauth2client/client.py", line 533, in apply
    headers['Authorization'] = 'Bearer ' + self.access_token
TypeError: cannot concatenate 'str' and 'NoneType' objects

```

Example scripts [get\_report\_fields.py](https://code.google.com/p/google-api-ads-python/source/browse/trunk/examples/adspygoogle/adwords/v201306/reporting/get_report_fields.py) and [get\_campaign\_stats.py](https://code.google.com/p/google-api-ads-python/source/browse/trunk/examples/adspygoogle/adwords/v201306/reporting/get_campaign_stats.py) work fine but [download\_criteria\_report.py](https://code.google.com/p/google-api-ads-python/source/browse/trunk/examples/adspygoogle/adwords/v201306/reporting/download_criteria_report.py) and [download\_criteria\_report\_with\_awql.py](https://code.google.com/p/google-api-ads-python/source/browse/trunk/examples/adspygoogle/adwords/v201306/reporting/download_criteria_report_with_awql.py) fail with the same error.

Any ideas?

My code:

```
#!/usr/bin/env python

import csv
import os
import MySQLdb as mdb
from adspygoogle.adwords.AdWordsClient import AdWordsClient

MATCH_TYPES = {
    'b': 'Broad',
    'e': 'Exact',
    'p': 'Phrase',
}

DEVICE_TYPES = {
    'c': 'Desktop',
    'm': 'Mobile',
    't': 'Tablet',
}

REPORT_TYPE = 'CREATIVE_CONVERSION_REPORT'

def download_report(client, client_id):
    # Initialize appropriate service.
    report_downloader = client.GetReportDownloader(version='v201306')

    # Create report query.
    report_query = ('SELECT AdGroupId', 'CampaignId', 'CreativeId FROM CREATIVE_CONVERSION_REPORT  DURING LAST_7_DAYS')

    path = '/tmp/report_%d.csv' % client_id
    file_path = report_downloader.DownloadReportWithAwql(report_query, 'CSV', file_path=path)

    print 'Report was downloaded to \'%s\'.' % file_path

if __name__ == '__main__':
    client = AdWordsClient()

    conn = mdb.connect('xxx.us-east-1.rds.amazonaws.com', 'xxx', 'xxx', 'xxx');
    with conn:
        cur = conn.cursor(mdb.cursors.DictCursor)
        cur.execute("SELECT * FROM xxx.adwords_accounts")

        rows = cur.fetchall()
        for row in rows:
            client_id = row['id']
            client.SetClientCustomerId(client_id)
            download_report(client, client_id)

```