treewide: replace error comparisons and assertions with errors.Is

Change-Id: Id2424eb155f2c6842c72c5fafd124d428ef901f2
Reviewed-on: https://review.monogon.dev/c/monogon/+/2994
Tested-by: Jenkins CI
Reviewed-by: Serge Bazanski <serge@monogon.tech>
diff --git a/metropolis/test/e2e/k8s_cts/main.go b/metropolis/test/e2e/k8s_cts/main.go
index 4b86b64..6383cb8 100644
--- a/metropolis/test/e2e/k8s_cts/main.go
+++ b/metropolis/test/e2e/k8s_cts/main.go
@@ -21,6 +21,7 @@
 
 import (
 	"context"
+	"errors"
 	"io"
 	"log"
 	"os"
@@ -159,7 +160,7 @@
 					log.Printf("Log pump error: %v", err)
 				}
 				logs.Close()
-			} else if err == ctx.Err() {
+			} else if errors.Is(err, ctx.Err()) {
 				return // Exit if the context has been cancelled
 			} else {
 				log.Printf("Pod logs not ready yet: %v", err)
@@ -170,7 +171,7 @@
 	for {
 		time.Sleep(1 * time.Second)
 		pod, err := clientSet.CoreV1().Pods("default").Get(ctx, podName, metav1.GetOptions{})
-		if err != nil && err == ctx.Err() {
+		if err != nil && errors.Is(err, ctx.Err()) {
 			return // Exit if the context has been cancelled
 		} else if err != nil {
 			log.Printf("Failed to get CTS pod: %v", err)
diff --git a/metropolis/test/util/runners.go b/metropolis/test/util/runners.go
index 99de4f1..a34c070 100644
--- a/metropolis/test/util/runners.go
+++ b/metropolis/test/util/runners.go
@@ -30,7 +30,7 @@
 				launch.Log("Test: %s: okay after %.1f seconds", name, time.Since(start).Seconds())
 				return
 			}
-			if err == ctx.Err() {
+			if errors.Is(err, ctx.Err()) {
 				t.Fatal(lastErr)
 			}
 			if errors.Is(err, &PermanentError{}) {