Deleting branch reports error even when it succeeds

[louisrigot]

repo.branch("foo")
# branch foo now exists
repo.branch("foo", delete=True)
# branch foo is deleted

However, doltpy reports:

doltpy.core.dolt.DoltException: (['dolt', 'branch', '--delete', 'foo', 'f', 'o', 'o'], b'', b"fatal: branch 'foo' not found\n", 1)