If users run "terraform import" in a directory with no Terraform
configuration files, it's likely that they've made a mistake either by
being in the wrong directory or forgetting to use the -config option
on the command line.
To help users find their mistake in this case, we'll now produce a
specialized error message for this situation:
Error: No Terraform configuration files
The directory /home/user/example does not contain any Terraform
configuration files (.tf or .tf.json). To specify a different
configuration directory, use the -config="..." command line option.
While here, this also converts some of the other existing messages to
diagnostics so that we can show any configuration warnings along with
the error message, and move towards the new standard error presentation.