Error locking state: Error acquiring the state lock: ConditionalCheckFailedException: The conditional request failed
status code: 400, request id:

ID: 222Whatever-222Whatever-222Whatever-d86c-222Whatever
Path: terraform.tfstate
Operation: OperationTypePlan
Who: username@hostname
Version: 0.11.7
Created: 2018-09-27 15:02:22.226277904 +0000 UTC
Info:

Terraform acquires a state lock to protect the state from being written
by multiple users at the same time. Please resolve the issue above and try
again. For most commands, you can disable locking with the “-lock=false”
flag, but this is not recommended.

Fix:

terraform force-unlock 222Whatever-222Whatever-222Whatever-d86c-222Whatever . # this is the ID provided in Error message