Terraform destroy fails on taint.

target.null_resource.log

$ terraform destroy --target=aws_instance.agent[2] --target=null_resource.agent[2]
data.external.whoami: Refreshing state...
data.template_file.os-setup: Refreshing state...
data.template_file.aws_ami: Refreshing state...
data.template_file.aws_ami_user: Refreshing state...
aws_vpc.default: Refreshing state... (ID: vpc-66567f00)
aws_security_group.any_access_internal: Refreshing state... (ID: sg-8c8ed7f1)
aws_subnet.private: Refreshing state... (ID: subnet-bb51c2f3)
aws_security_group.admin: Refreshing state... (ID: sg-3582db48)
aws_security_group.private_slave: Refreshing state... (ID: sg-fa84dd87)
aws_subnet.public: Refreshing state... (ID: subnet-2dc9ba4b)
aws_security_group.master: Refreshing state... (ID: sg-c982dbb4)
aws_security_group.public_slave: Refreshing state... (ID: sg-9084dded)
data.template_file.cluster-name: Refreshing state...
aws_s3_bucket.dcos_bucket: Refreshing state... (ID: mbernadin-tf4dcf-bucket)
aws_instance.agent[2]: Refreshing state... (ID: i-03833fcfcfa9ceaae)
aws_instance.public-agent: Refreshing state... (ID: i-0ab984d1b6f642dd8)
aws_instance.master[2]: Refreshing state... (ID: i-0574035b7347e08a8)
aws_instance.master[1]: Refreshing state... (ID: i-0ef7883f41c6cad79)
aws_instance.master[0]: Refreshing state... (ID: i-0e170f3c1c5ea44a5)
aws_instance.bootstrap: Refreshing state... (ID: i-0681529ca22cfd1dc)
data.template_file.script: Refreshing state...
aws_elb.internal-master-elb: Refreshing state... (ID: mbernadin-tf4dcf-int-master-elb)
data.template_file.script: Refreshing state...
null_resource.bootstrap: Refreshing state... (ID: 7097599696665734349)
null_resource.agent[2]: Refreshing state... (ID: 3747375853073314125)

An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
  - destroy

Terraform will perform the following actions:

  - aws_instance.agent[2]

  - null_resource.agent[0]

  - null_resource.agent[1]

  - null_resource.agent[2]

  - null_resource.agent[3]

  - null_resource.agent[4]

  - null_resource.agent[5]

  - null_resource.bootstrap

  - null_resource.master[0]

  - null_resource.master[1]

  - null_resource.master[2]

  - null_resource.public-agent


Plan: 0 to add, 0 to change, 12 to destroy.

Do you really want to destroy?
  Terraform will destroy all your managed infrastructure, as shown above.
  There is no undo. Only 'yes' will be accepted to confirm.

  Enter a value: n


Error: Destroy cancelled.