[MCL-1905] legacy.json missing causing java.io.FileNotFoundException

Potential Cause

This Issue is potentially caused by Antivirus Programs and/or Firewall Programs, especially Norton. Try disabling it while launching Minecraft and see if it helps. If it does maybe consider using a different Antivirus Program.

Also, this issue might easily be fixed by reinstalling Minecraft.

[17:00:51 WARN]: No assets index file C:\Users\Manuel-7\AppData\Roaming\.minecraft\assets\virtual\legacy; can't reconstruct assets

java.io.FileNotFoundException: File '/Users/test/Library/Application Support/minecraft/assets/indexes/legacy.json' does not exist
	at org.apache.commons.io.FileUtils.openInputStream(FileUtils.java:299) ~[launcher.jar:?]
	at org.apache.commons.io.FileUtils.readFileToString(FileUtils.java:1711) ~[launcher.jar:?]
	at net.minecraft.launcher.GameLauncher.getAssetObject(GameLauncher.java:323) ~[launcher.jar:?]
	at net.minecraft.launcher.GameLauncher.launchGame(GameLauncher.java:245) ~[launcher.jar:?]
	at net.minecraft.launcher.GameLauncher.onDownloadJobFinished(GameLauncher.java:616) [launcher.jar:?]
	at net.minecraft.launcher.updater.download.DownloadJob.popAndDownload(DownloadJob.java:120) [launcher.jar:?]
	at net.minecraft.launcher.updater.download.DownloadJob.access$000(DownloadJob.java:12) [launcher.jar:?]
	at net.minecraft.launcher.updater.download.DownloadJob$1.run(DownloadJob.java:89) [launcher.jar:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:439) [?:1.6.0_65]
	at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) [?:1.6.0_65]
	at java.util.concurrent.FutureTask.run(FutureTask.java:138) [?:1.6.0_65]
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895) [?:1.6.0_65]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918) [?:1.6.0_65]
	at java.lang.Thread.run(Thread.java:695) [?:1.6.0_65]

Related crash log:

Macs:
devconsole01.txt
devconsole02.txt

Windows:
devconsole03.txt