"error: expected `string literal` or `expression` after `=`" on Rust 1.41.1

[Tom Parker-Shemilt]

On Rust 1.41.1 cargo build on the v0.5.0 tag seems to work fine, but cargo install mdbook-linkcheck doesn't.

Compiling mdbook-linkcheck v0.5.0
error: expected `string literal` or `expression` after `=`
  --> /Users/palfrey/.cargo/registry/src/github.com-1ecc6299db9ec823/mdbook-linkcheck-0.5.0/src/bin/mdbook-linkcheck.rs:47:25
   |
47 |         possible_values = &["always", "auto", "never"]
   |                         ^

error: aborting due to previous error

error: failed to compile `mdbook-linkcheck v0.5.0`, intermediate artifacts can be found at `/var/folders/hs/z7c0cksd5nz80mjhc2qncx900000gn/T/cargo-installal8i6p`

Caused by:
  could not compile `mdbook-linkcheck`.

[Tom Parker-Shemilt]

I can also make this break with cargo install --path . on both v0.5.0 and master

[Tom Parker-Shemilt]

This appears to be a structopt issue. Compiling with structopt up to 0.3.7 works fine, but not 0.3.8 or 0.3.9

[Tom Parker-Shemilt]

I've filed this upstream TeXitoi/structopt#354

[Tom Parker-Shemilt]

No longer needed now TeXitoi/structopt@530eb22 yanked the broken versions