providers/aws: Fix issue with VPC Classic Link and regions that don't support it

- use eu-central-1 to a config to check for #4874
- update documentation

builtin/providers/aws/resource_aws_vpc.go

@@ -179,18 +179,27 @@ func resourceAwsVpcRead(d *schema.ResourceData, meta interface{}) error {
 	DescribeClassiclinkOpts := &ec2.DescribeVpcClassicLinkInput{
 		VpcIds: []*string{&vpcid},
 	}
+
+	// Classic Link is only available in regions that support EC2 Classic
 	respClassiclink, err := conn.DescribeVpcClassicLink(DescribeClassiclinkOpts)
 	if err != nil {
+		if awsErr, ok := err.(awserr.Error); ok && awsErr.Code() == "UnsupportedOperation" {
+			log.Printf("[WARN] VPC Classic Link is not supported in this region")
+		} else {
 			return err
 		}
+	} else {
 		classiclink_enabled := false
 		for _, v := range respClassiclink.Vpcs {
 			if *v.VpcId == vpcid {
+				if v.ClassicLinkEnabled != nil {
 					classiclink_enabled = *v.ClassicLinkEnabled
+				}
 				break
 			}
 		}
 		d.Set("enable_classiclink", classiclink_enabled)
+	}
 
 	// Get the main routing table for this VPC
 	// Really Ugly need to make this better - rmenn

builtin/providers/aws/resource_aws_vpc_test.go

@@ -264,6 +264,10 @@ resource "aws_vpc" "bar" {
 `
 
 const testAccVpcConfig_BothDnsOptions = `
+provider "aws" {
+	region = "eu-central-1"
+}
+
 resource "aws_vpc" "bar" {
 	cidr_block = "10.2.0.0/16"
 

website/source/docs/providers/aws/r/vpc.html.markdown

@@ -41,7 +41,9 @@ The following arguments are supported:
 * `instance_tenancy` - (Optional) A tenancy option for instances launched into the VPC
 * `enable_dns_support` - (Optional) A boolean flag to enable/disable DNS support in the VPC. Defaults true.
 * `enable_dns_hostnames` - (Optional) A boolean flag to enable/disable DNS hostnames in the VPC. Defaults false.
-* `enable_classiclink` - (Optional) A boolean flag to enable/disable ClassicLink for the VPC. Defaults false.
+* `enable_classiclink` - (Optional) A boolean flag to enable/disable ClassicLink 
+  for the VPC. Only valid in regions and accounts that support EC2 Classic.
+  See the [ClassicLink documentation][1] for more information. Defaults false.
 * `tags` - (Optional) A mapping of tags to assign to the resource.
 
 ## Attributes Reference
@@ -59,3 +61,6 @@ The following attributes are exported:
      [`aws_main_route_table_association`](/docs/providers/aws/r/main_route_table_assoc.html).
 * `default_network_acl_id` - The ID of the network ACL created by default on VPC creation
 * `default_security_group_id` - The ID of the security group created by default on VPC creation
+
+
+[1]: http://docs.aws.amazon.com/fr_fr/AWSEC2/latest/UserGuide/vpc-classiclink.html