Apply review remarks

Author: Kobzol

src/ci/citool/src/cpu_usage.rs

@@ -14,6 +14,8 @@ pub fn load_cpu_usage(path: &Path) -> anyhow::Result<Vec<f64>> {
         if cols.len() == 2 {
             if let Ok(idle) = cols[1].parse::<f64>() {
                 entries.push(100.0 - idle);
+            } else {
+                eprintln!("Warning: cannot parse CPU CSV entry {}", cols[1]);
             }
         }
     }

src/ci/citool/src/utils.rs

@@ -7,6 +7,5 @@ pub fn load_env_var(name: &str) -> anyhow::Result<String> {
 }
 
 pub fn read_to_string<P: AsRef<Path>>(path: P) -> anyhow::Result<String> {
-    let error = format!("Cannot read file {:?}", path.as_ref());
-    std::fs::read_to_string(path).context(error)
+    std::fs::read_to_string(&path).with_context(|| format!("Cannot read file {:?}", path.as_ref()))
 }