Exit with error if UI input scan fails

[awsiv]

UPDATE: adding -input=false seems to do the trick as pointed out here. It might still make sense to keep the error handling though?

---

Fixes: #26508

Sample output:

Step 4/4 : RUN TF_LOG=DEBUG /terraform plan /tmp/
 ---> Running in f67cf0c83d8d
2020/10/07 20:12:22 [WARN] Log levels other than TRACE are currently unreliable, and are supported only for backward compatibility.
  Use TF_LOG=TRACE to see Terraform's internal logs.
  ----
2020/10/07 20:12:22 [INFO] Terraform version: 0.14.0 dev 
2020/10/07 20:12:22 [INFO] Go runtime version: go1.15.2
2020/10/07 20:12:22 [INFO] CLI args: []string{"/terraform", "plan", "/tmp/"}
2020/10/07 20:12:22 [DEBUG] Attempting to open CLI config file: /root/.terraformrc
2020/10/07 20:12:22 [DEBUG] File doesn't exist, but doesn't need to. Ignoring.
2020/10/07 20:12:22 [DEBUG] ignoring non-existing provider search directory terraform.d/plugins
2020/10/07 20:12:22 [DEBUG] ignoring non-existing provider search directory /root/.terraform.d/plugins
2020/10/07 20:12:22 [DEBUG] ignoring non-existing provider search directory /root/.local/share/terraform/plugins
2020/10/07 20:12:22 [DEBUG] ignoring non-existing provider search directory /usr/local/share/terraform/plugins
2020/10/07 20:12:22 [DEBUG] ignoring non-existing provider search directory /usr/share/terraform/plugins
2020/10/07 20:12:22 [INFO] CLI command args: []string{"plan", "/tmp/"}
2020/10/07 20:12:22 [WARN] Log levels other than TRACE are currently unreliable, and are supported only for backward compatibility.
  Use TF_LOG=TRACE to see Terraform's internal logs.
  ----
2020/10/07 20:12:22 [DEBUG] New state was assigned lineage "ac8d3306-0318-ef71-e700-fc02993b217c"
2020/10/07 20:12:22 [DEBUG] checking for provisioner in "."
2020/10/07 20:12:22 [DEBUG] checking for provisioner in "/"
2020/10/07 20:12:22 [INFO] Failed to read plugin lock file .terraform/plugins/linux_amd64/lock.json: open .terraform/plugins/linux_amd64/lock.json: no such file or directory
2020/10/07 20:12:22 [INFO] backend/local: starting Plan operation
2020/10/07 20:12:22 [DEBUG] backend/local: will prompt for input of unset required variables [test]
2020/10/07 20:12:22 [DEBUG] command: asking for input: "var.test"
2020/10/07 20:12:22 [ERR] UIInput scan err: EOF
2020/10/07 20:12:22 [WARN] backend/local: Failed to request user input for variable "test": EOF
var.test
  Enter a value: e:
Error: No value for required variable

  on tmp/test.tf line 1:
   1: variable "test"{}

The root module input variable "test" is not set, and has no default value.
Use a -var or -var-file command line argument to provide a value for this
variable.

The command '/bin/sh -c TF_LOG=DEBUG /terraform plan /tmp/' returned a non-zero code: 1

[hashicorp-cla]

All committers have signed the CLA.

[alisdair]

This fix makes sense to me, thanks! 🎉

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

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