Make hidden lifetime parameters explicit

With a recent Rust version upgrade hidden lifetime parameters cause a
warning of the form:
  > warning: hidden lifetime parameters in types are deprecated
  >   --> src/error.rs:58:25
  >    |
  > 58 |   fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
  >    |                         ^^^^^^^^^^^^^^- help: indicate the anonymous lifetime: `<'_>`

This change adjusts the code to make those lifetimes explicit (while
keeping them anonymous).

0 files changed, 0 insertions, 0 deletions