Macro slog_scope::slog_warn

macro_rules! slog_warn {
    ( $ l : expr , # $ tag : expr , $ ( $ args : tt ) + ) => { ... };
    ( $ l : expr , $ ( $ args : tt ) + ) => { ... };
}

Log warning level record (alias)

Prefer shorter version, unless it clashes with existing log crate macro.

See slog_log for documentation.