Symptoms: after successful upload, the build is made unavailable in Itunes Connect, and an email is sent with the message in title.
Similar errors: ITMS-90542, but this is different in that no ITMS error is specified. Also, the key mentioned has the correct value, so that there is nothing to fix.
Result: an app that uploaded fine before Sep 22 can no longer be updated.
What have you tried: Up-/downgrading XCode and Application Loader, modified the mentioned key, uploaded many versions of a simple test application to pinpoint the cause.
Cause: one or both of CFBundleExecutable and CFBundleName keys contain a correctly encoded character 'å'. Likely, other correctly encoded non-ASCII characters cause the same misleading message.
Solution: Set one or both of the keys to contain only ASCII characters, until the problem is addressed by Apple. The CFBundleDisplayName key is handled correctly, so that you can keep your app's original display name.
Discussion: The new Itunes Connect processing module's parser breaks on non-ASCII characters in one or both of these keys, leading it to reject updates to a validated and previously approved app with identical info.plist content, and e-mail an incorrect message stating that the CFBundleSupportedPlatforms key is in error, when it is not. It may be productive to suspect a similar cause for other rejections/e-mails when the ITMS error number is not specified, rather than spend time trouble-shooting the cited error.