dotcloud/docker — pull request #5782 by unclejack (2014-05-13 19:03:45+00:00)
Title: detect inaccessible files & dirs before uploading context

Fixes #5270

This PR fixes 5270 by throwing an error when the Docker cli client can't access some files from the context.
This can save a lot of bandwidth and time when working with remote Docker daemons running on other hosts.