Error checking simplifications (#3694)

Signed-off-by: Denis O <denis.o@linux.com>

internal/command/e2etest/provider_oci_mirrors_test.go

@@ -91,9 +91,6 @@ func TestProviderOCIMirrors(t *testing.T) {
 		}
 	`, registryAddr)
 	t.Logf("cli config:\n%s", cliConfigSrc)
-	if err != nil {
-		t.Fatalf("failed to marshal temporary CLI configuration: %s", err)
-	}
 	err = os.WriteFile(cliConfigFile, []byte(cliConfigSrc), os.ModePerm)
 	if err != nil {
 		t.Fatalf("failed to create temporary CLI configuration file: %s", err)

internal/plans/planfile/tfplan_test.go

@@ -585,9 +585,5 @@ func TestTFPlanChangeReasonsEncoding(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-
-		if err != nil {
-			t.Fatal("should've succeeded, got error: ", err)
-		}
 	}
 }

internal/states/statefile/version3_upgrade.go

@@ -329,10 +329,10 @@ func upgradeInstanceObjectV3ToV4(_ *resourceStateV2, isOld *instanceStateV2, ins
 		instKeyRaw = int(tk)
 	case addrs.StringKey:
 		instKeyRaw = string(tk)
+	case nil:
+		// NoKey, so instKeyRaw remains nil
 	default:
-		if instKeyRaw != nil {
-			return nil, fmt.Errorf("unsupported instance key: %#v", instKey)
-		}
+		return nil, fmt.Errorf("unsupported instance key: %#v", instKey)
 	}
 
 	var attributes map[string]string