Function nix_compat::derivation::parse_error::into_nomerror

pub(crate) fn into_nomerror<I>(e: Err<Error<I>>) -> Err<NomError<I>>

This essentially implements From<nom::Err<nom::error::Error<I>>> for nom::Err<NomError<I>>, which we can’t because nom::Err<_> is a foreign type.