gsutil was working as a stand-alone on my system. Then I installed SDK, including some authentication stuff. Now gsutil says my credentials are invalid.
$ gcloud auth login wolfvolpi@gmail.com
WARNING: `gcloud auth login` no longer writes application default credentials.
If you need to use ADC, see:
gcloud auth application-default --help
You are now logged in as [redacted].
Your current project is [redacted]. You can change this setting by running:
$ gcloud config set project PROJECT_ID
$ gsutil ls
Your credentials are invalid. Please run
$ gcloud auth login
How to set my credentials so that gsutil runs again?
$ gcloud version
Google Cloud SDK 146.0.0
core 2017.02.28
core-nix 2017.02.28
gcloud
gcloud-deps 2017.02.28
gcloud-deps-linux-x86_64 2017.02.28
gsutil 4.22
gsutil-nix 4.22
If you previously had gsutil configured with credentials, it is possible that it is picking up those old credentials that will no longer work in the Cloud SDK mode. Take a look in your boto file (typically at ~/.boto) and remove any credentials found in there.
You can see the list of the valid fields in the boto file here: https://cloud.google.com/storage/docs/gsutil/commands/config#additional-configuration-controllable-features