I have the most pedestrian of a Terraform sample:

```
#  Configure AWS provider
provider "aws" {
    region     = "us-east-1"
    access_key = "xxxxxxxxx"
    secret_key = "yyyyyyyyyyy"
}

#  Terraform configuration
terraform {
  backend "s3" {
    bucket = "terraform.example.com"
    key    = "85/182/terraform.tfstate"
    region = "us-east-1"
  }
}

```

When I run terraform init I receive the following (traced) response:

```
2018/08/14 14:19:13 [INFO] Terraform version: 0.11.7  41e50bd32a8825a84535e353c3674af8ce799161
2018/08/14 14:19:13 [INFO] Go runtime version: go1.10.1
2018/08/14 14:19:13 [INFO] CLI args: []string{"C:\\cygwin64\\usr\\local\\bin\\terraform.exe", "init"}
2018/08/14 14:19:13 [DEBUG] Attempting to open CLI config file: C:\Users\judall\AppData\Roaming\terraform.rc
2018/08/14 14:19:13 [DEBUG] File doesn't exist, but doesn't need to. Ignoring.
2018/08/14 14:19:13 [INFO] CLI command args: []string{"init"}
2018/08/14 14:19:13 [DEBUG] command: loading backend config file: C:\cygwin64\home\judall\t2

2018/08/14 14:19:13 [DEBUG] command: no data state file found for backend config
Initializing the backend...
2018/08/14 14:19:13 [DEBUG] New state was assigned lineage "5113646b-318f-9612-5057-bc4803292c3a"
2018/08/14 14:19:13 [INFO] Building AWS region structure
2018/08/14 14:19:13 [INFO] Building AWS auth structure
2018/08/14 14:19:13 [INFO] Setting AWS metadata API timeout to 100ms
2018/08/14 14:19:13 [INFO] Ignoring AWS metadata API endpoint at default location as it doesn't return any instance-id

2018/08/14 14:19:13 [DEBUG] plugin: waiting for all plugin processes to complete...
Error configuring the backend "s3": No valid credential sources found for AWS Provider.
  Please see https://terraform.io/docs/providers/aws/index.html for more information on
  providing credentials for the AWS Provider

Please update the configuration in your Terraform files to fix this error
then run this command again.

```

I've been googling for hours on this. I've tried to use the 'profile' property - which yields slightly different trace logs, but the same end result. I've tried setting the AWS\_ environment variables - with the same result.

I'm running terraform version 0.11.7. Any suggestions?