While setting up a new job, I C&P my Git branch name into the "Branch Specifier" under SCM. I didn't realize it, but there was a trailing space in the branch name. This caused the build to fail with:

Started by user ryan.shoemaker
Building in workspace /opt/jenkins/jobs/MyJob/workspace
Checkout:workspace / /opt/jenkins/jobs/MyJob/workspace - hudson.remoting.LocalChannel@6c616408
Using strategy: Default
Wiping out workspace first.
Cloning the remote Git repository
Cloning repository origin
Fetching upstream changes from ssh://ryan.shoemaker@mygitserver.com/git/MyModule
ERROR: Couldn't find any revision to build. Verify the repository and branch configuration for this job.

When I removed the trailing space from the branch name, everything built fine.