Be a lot more conservative in _github_submodule_required#708

Eijebong merged 1 commit intotaskcluster:maintaskcluster/taskgraph:mainfrom

Eijebong:dont-assume-no-submodules-in-error-casesEijebong/taskgraph:dont-assume-no-submodules-in-error-casesCopy head branch name to clipboard