error: direct implementation of `ToString`
   --> src/sta/types.rs:128:1
    |
128 | / impl ToString for KeyMgmt {
129 | |     fn to_string(&self) -> String {
130 | |         match self {
131 | |             KeyMgmt::None => "NONE".to_string(),
...   |
136 | |     }
137 | | }
    | |_^
    |
    = help: prefer implementing `Display` instead
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#to_string_trait_impl
    = note: `-D clippy::to-string-trait-impl` implied by `-D clippy::all`
    = help: to override `-D clippy::all` add `#[allow(clippy::to_string_trait_impl)]`