Use IsTerminal in librustdoc

Cargo.lock

@@ -4272,7 +4272,6 @@ version = "0.0.0"
 dependencies = [
  "arrayvec",
  "askama",
- "atty",
  "expect-test",
  "itertools",
  "minifier",

src/librustdoc/Cargo.toml

@@ -9,7 +9,6 @@ path = "lib.rs"
 [dependencies]
 arrayvec = { version = "0.7", default-features = false }
 askama = { version = "0.11", default-features = false, features = ["config"] }
-atty = "0.2"
 itertools = "0.10.1"
 minifier = "0.2.2"
 once_cell = "1.10.0"

src/librustdoc/lib.rs

@@ -8,6 +8,7 @@
 #![feature(box_patterns)]
 #![feature(control_flow_enum)]
 #![feature(drain_filter)]
+#![feature(is_terminal)]
 #![feature(let_chains)]
 #![feature(test)]
 #![feature(never_type)]
@@ -69,7 +70,7 @@ extern crate jemalloc_sys;
 
 use std::default::Default;
 use std::env::{self, VarError};
-use std::io;
+use std::io::{self, IsTerminal};
 use std::process;
 
 use rustc_driver::abort_on_err;
@@ -180,7 +181,7 @@ fn init_logging() {
     let color_logs = match std::env::var("RUSTDOC_LOG_COLOR").as_deref() {
         Ok("always") => true,
         Ok("never") => false,
-        Ok("auto") | Err(VarError::NotPresent) => atty::is(atty::Stream::Stdout),
+        Ok("auto") | Err(VarError::NotPresent) => io::stdout().is_terminal(),
         Ok(value) => early_error(
             ErrorOutputType::default(),
             &format!("invalid log color value '{}': expected one of always, never, or auto", value),