Display nicer error when AWS_REGION is not set

[christophetd]

Currently:

2024/04/04 11:33:06 unable to run terraform apply on prerequisite: unable to create attack technique prerequisites. Ensure you are authenticated against AWS and have the right permissions to run Stratus Red Team.
Stratus Red Team will display below the error that Terraform returned:
unable to apply Terraform: exit status 1

Error: Missing required argument

  on main.tf line 10, in provider "aws":
  10: provider "aws" {

The argument "region" is required, but no definition was found.