[Lilypond-auto] Patchy report from grenouille

[grenouille]

20:30:12 (UTC) Begin LilyPond compile, previous commit at       
4c2851d28c0a94a30cc7652b9b0052ce7f0ade7e
20:30:13 *** FAILED STEP ***
        merge from staging
        Command '['git', 'branch', 'test-master-lock', 'origin/master']' 
returned non-zero exit status 128
fatal: A branch named 'test-master-lock' already exists.