In https://codereview.webrtc.org/1389963002 the message displayed when trying to create a CL from an unsupported location was improved. However it's confusing for developers working from a WebRTC checkout if they stand in src/webrtc when trying to create a CL. R=henrika@webrtc.org, phoglund@webrtc.org Review URL: https://codereview.webrtc.org/1432073002 . Cr-Commit-Position: refs/heads/master@{#10571}