eu-central-1 requires SignatureV4 method

[DenisBY]

otherwise I'm getting "AWS was not able to validate the provided access credentials"

[benholtz]

Same here. Some details and a link:
http://aws.amazon.com/blogs/aws/aws-region-germany/
For Developers – Signature Version 4 Support
This new Region supports only Signature Version 4. If you have built applications with the AWS SDKs or the AWS Command Line Interface (CLI) and your API calls are being rejected, you should update to the newest SDK and CLI. To learn more, visit Using the AWS SDKs and Explorers. @winebarrel