function warn(vFile, sMessage) {
		var sFileName = typeof vFile === "string"
				? vFile
				: aFileNames[vFile];

		jQuery.sap.log.warning(sMessage, sFileName, "sap.ui.test.BranchTracking");
		_$blanket[sFileName].warnings.push(sMessage);
	}
Logs the given message related to the given file both as a warning on console and as a
warning to be reported inside QUnit.module's "before" hook.

@param {number|string} vFile - the affected file's index or name
@param {string} sMessage - a message