Note that service account creation is eventually consistent.

third_party/terraform/website/docs/r/google_service_account.html.markdown

@@ -10,6 +10,11 @@ description: |-
 
 Allows management of a [Google Cloud Platform service account](https://cloud.google.com/compute/docs/access/service-accounts)
 
+-> Creation of service accounts is eventually consistent, and that can lead to
+errors when you try to apply IAM roles to service accounts immediately after
+creation. If using these resources in the same config, you can add a
+[`sleep` using `local-exec`](https://github.com/hashicorp/terraform/issues/17726#issuecomment-377357866).
+
 ## Example Usage
 
 This snippet creates a service account, then gives it objectViewer