RUSTSEC-2020-0036: failure is officially deprecated/unmaintained

[github-actions]

failure is officially deprecated/unmaintained

Details
Status	unmaintained
Package	failure
Version	0.1.8
URL	rust-lang-deprecated/failure#347
Date	2020-05-02

The failure crate is officially end-of-life: it has been marked as deprecated
by the former maintainer, who has announced that there will be no updates or
maintenance work on it going forward.

The following are some suggested actively developed alternatives to switch to:

• anyhow
• eyre
• fehler
• snafu
• thiserror

See advisory page for additional details.

[fmorency]

This is caused by the fmerk crate which use the deprecated failure crate.

The current fmerk master doesn't solve the problem.

We should probably fork the project and replace the crate from there.