fix usage of debug formatters

crates/core/src/config.rs

@@ -23,7 +23,7 @@ impl Config {
 
         if let Err(e) = from_file {
             if e.kind() == ErrorKind::NotFound {
-                println!("creating default config under {file:?}");
+                println!("creating default config under {}", file.to_string_lossy());
                 return Self::use_default_and_save_to(file);
             } else {
                 bail!("unexpected error occured: {e:?}");

crates/core/src/core.rs

@@ -313,7 +313,10 @@ fn show_error(error: &anyhow::Error, backend: &dyn Backend) {
     match get_single_var("RUST_BACKTRACE") {
         Some(s) => {
             if s == "1" || s == "full" {
-                println!("WARNING: skipping backend '{section}': {error:?}\n");
+                eprintln!("WARNING: skipping backend '{section}':");
+                for err in error.chain() {
+                    eprintln!("  {err}");
+                }
             }
         }
         None => println!("WARNING: skipping backend '{section}': {error}"),

crates/core/src/grouping/group.rs

@@ -27,7 +27,10 @@ impl Group {
             let path = file.path();
 
             if config.warn_not_symlinks && !path.is_symlink() {
-                println!("WARNING: group file {path:?} is not a symlink");
+                println!(
+                    "WARNING: group file {} is not a symlink",
+                    path.to_string_lossy()
+                );
             }
 
             let group =
@@ -88,12 +91,14 @@ impl Group {
         let mut sections = HashSet::new();
 
         while lines.peek().is_some() {
-            match Section::try_from_lines(&mut lines).context("reading section") {
+            let result = Section::try_from_lines(&mut lines).context("reading section");
+            match result {
                 Ok(section) => {
                     sections.insert(section);
                 }
                 Err(e) => {
-                    println!("WARNING: could not process a section under group '{name}': {e:?}\n");
+                    let err = e.root_cause();
+                    println!("WARNING: could not process a section under group '{name}': {err}");
                 }
             }
         }

crates/core/src/grouping/section.rs

@@ -45,7 +45,7 @@ impl Section {
             }
         }
 
-        ensure!(!packages.is_empty());
+        ensure!(!packages.is_empty(), "[{name}] is empty");
 
         Ok(Self::new(name, packages))
     }