Acceptance tests do not source region from named profile

[gdavison]

When using the environment variable AWS_PROFILE to authenticate with a named profile, the acceptance tests retrieve the correct credentials but do not use the region configured on the profile.

For example, with

~/.aws/credentials

[example]
aws_access_key_id = ...
aws_secret_access_key = ...
region = <some region>

I get

$ AWS_PROFILE=example make testacc PKG=ecs TESTS=TestAccECSService_

    service_test.go:566: Step 1/2 error: Error running pre-apply refresh: exit status 1
        
        Error: Invalid provider configuration
        
        Provider "registry.terraform.io/hashicorp/aws" requires explicit
        configuration. Add a provider block to the root module and configure the
        provider's required arguments as described in the provider documentation.
        
        
        Error: error configuring Terraform AWS Provider: error validating provider credentials: error calling sts:GetCallerIdentity: operation error STS: GetCallerIdentity, https response error StatusCode: 403, RequestID: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx, api error InvalidClientTokenId: The security token included in the request is invalid.

Passing the region in AWS_REGION is a workaround.