The following forum message was posted by Anonymous at http://sourceforge.net/projects/s3tools/forums/forum/618865/topic/3825692:
Before you build via python ./setup.py install modify the ../S3/S3.py file after
line 409 and add this line (as 410):
headers['content-length'] = '' + str(headers['content-length']) + ''
The extra '' quotes are not needed but just added to illustrate what's going
on here...it will also work if you just copy that line too. Make sure your
indentations line up (2 tabs in my case on linux).
The issue has to do with the content-length value being set to 0 as an integer.
It needs to evaluate as a string for the next call. Listing the root of your
S3:// buckets is the sample test on configuring so it 'appears' that it fails,
although it really is likely setup properly.
Hope this helps someone else. No need to revert back to 2.6 or 2.5 if you need
2.7 for other items on your system.