The current implementation of s3 signature calculation
rely on WSGI Url encoding which is discouraged by AWS:
https://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-header-based-auth.html.
This leads to reject requests with valid signature.
This update encode only characters specified by AWS except
'A'-'Z', 'a'-'z', '0'-'9', '-', '.', '_', and '~' to comply
AWS signature calculation.
Fixes LP Bug #1961841
Change-Id: Ifa8f94544224c3379e7f2805f6f86d0b0a47279a
cb8b3cdab2