When's Eric Holder's trial?

You can be convicted of contempt of Congress. That doesn't mean you will be.

Unlike Bannon, Holder was able to offer a defense of his refusal to respond to the subpoena - a claim that the materials in question were privileged from being demanded by Congress. That makes it nearly impossible to establish the mens rea requirement of a criminal charge - if Holder is operating under a belief that the documents are subject to Executive Privilege, then getting a conviction will be nearly impossible.

Unlike Steve Bannon, Congressional efforts to subpoena an Executive official reflect a conflict between the branches of government - and the courts are generally not available to resolve those disputes. That's why the courts ruled that there was no judicial remedy available to Congress when then-President Trump ordered Don McGahn not to cooperate with a House subpoena:

nytimes.com - Mcgahn subpoena trump

When Congress exercises its subpoena power against private citizens, like Bannon, that's not in play.