Please see: wiki on GitHub
You are probably using Python 2.3 or older, however s3cmd only supports Python 2.4 or newer.
This is an old error in s3cmd that is now fixed. Please upgrade to s3cmd 0.9.8.4 or later.
S3cmd 0.9.5 added support for buckets created in European Amazon data center. Unfortunately the change has broken access to existing buckets with upper-case characters in their names. This regression has long stayed unnoticed and has only recently been fixed in s3cmd 0.9.8.4.
Therefore if you are suddenly getting errors like:
ERROR: S3 error: 403 (Forbidden): SignatureDoesNotMatch
after upgrading from s3cmd 0.9.4 or older to 0.9.5 or newer, you are advised to upgrade even further to s3cmd 0.9.8.4 or newer to regain access to your upper-case named buckets.
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