Sync: don't log "fatal" errors when nothing is really wrong

[isc-tleavitt]

Example:

Syncing local repository...

Fetch done
Pulling from branch: test-reload-behavior
fatal: couldn't find remote ref test-reload-behavior


Nothing to compile.

fatal: couldn't find remote ref test-reload-behavior

Pull ran with return code: 1
remote: 
remote: To create a merge request for test-reload-behavior, visit:        
remote:   https://scm.dev.isccloud.io/appservices/appservices/-/merge_requests/new?merge_request%5Bsource_branch%5D=test-reload-behavior        
remote: 
To [https://scm.dev.isccloud.io/appservices/appservices.git](https://scm.dev.isccloud.io/appservices/appservices.git%3Cbr%3E)
 * [new branch]      test-reload-behavior -> test-reload-behavior

Current branch test-reload-behavior is up to date.

Nothing to compile.
Everything up-to-date

In this case, the fact that the remote ref can't be found is actually totally fine. We shouldn't log errors about it as a nontechnical user (or even a technical user) might be reasonably scared by seeing "fatal" in a log!

(A user noted this and I've just seen it again.)