provider/aws: output the log group name when create fails (#11812)

* provider/aws: output the log group name when create fails

* adjusted formatting to match other error output

* fixup detailed error message for ResourceAlreadyExistsException

* forgot an import

* show the log group name regardless of error type

builtin/providers/aws/resource_aws_cloudwatch_log_group.go

@@ -7,6 +7,7 @@ import (
 	"github.com/hashicorp/terraform/helper/schema"
 
 	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/cloudwatchlogs"
 	"github.com/hashicorp/errwrap"
 )
@@ -54,7 +55,10 @@ func resourceAwsCloudWatchLogGroupCreate(d *schema.ResourceData, meta interface{
 		LogGroupName: aws.String(d.Get("name").(string)),
 	})
 	if err != nil {
-		return fmt.Errorf("Creating CloudWatch Log Group failed: %s", err)
+		if awsErr, ok := err.(awserr.Error); ok && awsErr.Code() == "ResourceAlreadyExistsException" {
+			return fmt.Errorf("Creating CloudWatch Log Group failed: %s:  The CloudWatch Log Group '%s' already exists.", err, d.Get("name").(string))
+		}
+		return fmt.Errorf("Creating CloudWatch Log Group failed: %s '%s'", err, d.Get("name"))
 	}
 
 	d.SetId(d.Get("name").(string))