Since AWS-SDK 1.5.3  the library automatically checks for credentials. This makes it unnecessary to supply credentials when they are present in environment variables or supplied via an IAM Instance Profile.  http://aws.amazon.com/releasenotes/Ruby/0304005114813505
The ":" is a special character in file paths passed to ImageMagick's "identify" command. Even though Cocaine (and everything else in paperclip) escapes special characters correctly, we need to strip it out of filenames to ensure identify (and probably other ImageMagick commands) can run correctly.
…ated and throws a warning.