A request path with an invalid percent escape, such as "/bucket/%zz",
failed url.PathUnescape in the DecodeURL middleware and the raw error
was answered with 500 InternalError. S3 rejects such a request with
400 InvalidURI.
Return InvalidURI from DecodeURL, so the s3 and admin routers answer
with it as well, and let the website handler pass the error through
instead of mapping it on its own.
Fixes#2070
dualfroz
upstream