"filename_effective" is not a valid template control keyword.

```
There are some problems with the configuration, described below.

The Terraform configuration must be valid before initialization so that
Terraform can determine which modules and providers need to be installed.

Error: Invalid template control keyword

on .terraform/modules/elasticsearch_cleanup.artifact/main.tf line 2, in data "external" "curl":
2: program = ["curl", "${var.curl_arguments}", "--write-out", "{\"success\": \"true\", \"filename_effective\": \"%{filename_effective}\"}", "-o", "${local.output_file}", "${local.url}"]

"filename_effective" is not a valid template control keyword.

Error: Unsuitable value type

on .terraform/modules/elasticsearch_cleanup.artifact/variables.tf line 11, in variable "module_path":
11: description = "Local path to the terraform module; e.g. `${path.module}`"

Unsuitable value: value must be known

Error: Variables not allowed

on .terraform/modules/elasticsearch_cleanup.artifact/variables.tf line 11, in variable "module_path":
11: description = "Local path to the terraform module; e.g. `${path.module}`"

Variables may not be used here.
```

After a clean `terraform init`. I am using `?ref=tags/0.4.0`