cli: Don't emit ANSI codes to stderr

It seems the tracing crate is broken in this respect. Digging
through best practices, `anstream` is used by clap and looks sane.
We're basically just following their example.

Signed-off-by: Colin Walters <walters@verbum.org>

cli/Cargo.toml

@@ -14,11 +14,13 @@ default-run = "bootc"
 platforms = ["*-unknown-linux-gnu"]
 
 [dependencies]
+anstream = { workspace = true }
 anyhow = { workspace = true }
 bootc-lib = { version = "1.0", path = "../lib" }
 bootc-utils = { path = "../utils" }
 tokio = { workspace = true, features = ["macros"] }
 log = "0.4.21"
+owo-colors = { workspace = true }
 tracing = { workspace = true }
 
 [lints]

cli/src/main.rs

@@ -1,5 +1,8 @@
 //! The main entrypoint for bootc, which just performs global initialization, and then
 //! calls out into the library.
+//!
+use std::io::Write as _;
+
 use anyhow::Result;
 
 /// The code called after we've done process global init and created
@@ -32,11 +35,15 @@ fn run() -> Result<()> {
 }
 
 fn main() {
+    use owo_colors::OwoColorize;
+
     // In order to print the error in a custom format (with :#) our
     // main simply invokes a run() where all the work is done.
     // This code just captures any errors.
     if let Err(e) = run() {
-        tracing::error!("{:#}", e);
+        let mut stderr = anstream::stderr();
+        // Don't panic if writing fails
+        let _ = writeln!(stderr, "{}{:#}", "error: ".red(), e);
         std::process::exit(1);
     }
 }