I think it's fair to say that fehler has been a success. Apparently (#66) aren't able to work on this right now, which is sad.
The way that cargo works means that it is quite disruptive to change the crate name. (It's particularly annoying for downstreams like Debian who curate and do release management.)
Would you consider granting co-ownership of the crate name fehler (and fehler-macros) on crates.io to @Nemo157? (I'm also willing to be a crate owner to help reduce bus factor but I don't have tuits right now for reviewing work on fehler.)