ads-github-merge-all-upstreams: stderr message on failed ff merge indicates "bailing out", which is not always true

[salewski]

When the ads-github-merge-all-upstream tool's '-k' (--keep-going) option
is speecified and a fast-forward merge is not possible for some reason, an
'error' message is emitted indicating that the program is "bailing out":

$ ads-github-merge-all-upstreams -vkpp
...
ads-github-merge-all-upstreams (info): [repo: "foobar"] currently checked-out branch ("master") is the default branch (no need for checkout)
fatal: Not possible to fast-forward, aborting.
ads-github-merge-all-upstreams (error): [repo: "foobar"] was error while attempting to merge 'upstream/master'; bailing out
ads-github-merge-all-upstreams (warning): '-k' (--keep-going) specified; continuing
ads-github-merge-all-upstreams (info): [repo: "bazqux"] currently checked-out branch ("master") is the default branch (no need for checkout)
Already up-to-date.
...

That message is correct for the default behavior of the program (when the
'-k' option is not specified, but when the '-k' option /is/ specified, the
message should not indicate that the program is "bailing out" -- it is not
correct, and gives the impression that the error detection is not working
correctly.