Add logs for iam server certificate delete conflict (#2533)

* Query elb API for load balancer arn causing delete conflict

- For IAM server certificate.

* Use regex for lb name.

* Edits for #2533

aws/resource_aws_iam_server_certificate.go

@@ -5,11 +5,13 @@ import (
 	"encoding/hex"
 	"fmt"
 	"log"
+	"regexp"
 	"strings"
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
+	"github.com/aws/aws-sdk-go/service/elb"
 	"github.com/aws/aws-sdk-go/service/iam"
 	"github.com/hashicorp/terraform/helper/resource"
 	"github.com/hashicorp/terraform/helper/schema"
@@ -180,6 +182,7 @@ func resourceAwsIAMServerCertificateDelete(d *schema.ResourceData, meta interfac
 		if err != nil {
 			if awsErr, ok := err.(awserr.Error); ok {
 				if awsErr.Code() == "DeleteConflict" && strings.Contains(awsErr.Message(), "currently in use by arn") {
+					currentlyInUseBy(awsErr.Message(), meta.(*AWSClient).elbconn)
 					log.Printf("[WARN] Conflict deleting server certificate: %s, retrying", awsErr.Message())
 					return resource.RetryableError(err)
 				}
@@ -209,6 +212,22 @@ func resourceAwsIAMServerCertificateImport(
 	return []*schema.ResourceData{d}, nil
 }
 
+func currentlyInUseBy(awsErr string, conn *elb.ELB) {
+	r := regexp.MustCompile(`currently in use by ([a-z0-9:-]+)\/([a-z0-9-]+)\.`)
+	matches := r.FindStringSubmatch(awsErr)
+	if len(matches) > 0 {
+		lbName := matches[2]
+		describeElbOpts := &elb.DescribeLoadBalancersInput{
+			LoadBalancerNames: []*string{aws.String(lbName)},
+		}
+		if _, err := conn.DescribeLoadBalancers(describeElbOpts); err != nil {
+			if isAWSErr(err, "LoadBalancerNotFound", "") {
+				log.Printf("[WARN] Load Balancer (%s) causing delete conflict not found", lbName)
+			}
+		}
+	}
+}
+
 func normalizeCert(cert interface{}) string {
 	if cert == nil || cert == (*string)(nil) {
 		return ""