Raises error during provision/update if no .tf files found

[smaly-amazon]

Description

Raises error during provision/update if no .tf files found

Testing

• python3 -m unittest on terraform_runner
• Service Catalog integration tests:Provision, update, and terminate
  • artifact with no .tf files in the root directory. Fails to provision and gives expected error message
  • Artifact with one .tf file in the root directory. Provisions successfully.
  • Artifact with multiple .tf files in the root directory. Provisions successfully.