It doesn't need to necessarily be until November. Just hold out on an indictment until after the Convention, when Hillary has been nominated and selected her VP. If she's indicted then and it looks bad, that basically gives the Democrats the ability to give the nomination to anyone they want (perhaps tipped by her selection of VP), rather than Bernie.
She doesn’t even need to be indicted. All the FBI has to do is recommend she BE indicted. I think at that point, Obama convinces her to drop out so the Justice Dept. doesn’t have to worry about indicting the party candidate. Then they can pick someone else, and he can quietly make the Hillary indictment go away. No one will care if she’s not on the ticket.