String interpolation not covered yet in unwrap exercise

[louwers]

For the Unwrap exercise string interpolation is needed.

Correct me if I'm wrong, but I don't think it's covered at that point.

[LukeMathWalker]

It is indeed correct.

At the same time, the naive panic!(err) attempt will lead to a compiler error that will spit out the correct solution:

error: format argument must be a string literal
 --> src/main.rs:3:12
  |
3 |     panic!(error);
  |            ^
  |
help: you might be missing a string literal to format with
  |
3 |     panic!("{}", error);
  |            +++++

Since we explicitly talk about interpolation two exercises down the line, I think it's a fine balance to strike.