Error: could not find or load main class net.minecraft.client.main.Main

When downloading new snapshot, game does not launch after the download, and I get the message

Error: Could not find or load main class net.minecraft.client.main.Main

Cannot play the game at all.

Launcher log shows:
finished downloading files,
finished successfully,
launching game,
unpacking natives,
launching in dir,
half command,
looking for orphaned versions to clean up,
game ended with bad state exit code 1,
showing launcher due to a game crash,
looking for old natives and assets to clean up,
deleting.

This repeats exactly every time I try to play.