Linguist path discovery still broken

Even with the changes in 3f252917, bundler can still output warnings to stdout when executing find_name.

For example, here is the output I am getting with gitaly-0.43.1 on NixOS, where I am getting warnings about Bundler version mismatches that are being interpreted by gitaly as part of the path.

Nov 13 02:55:16 davinci gitaly[19881]: time="2017-11-13T02:55:16Z" level=info msg="Starting Gitaly" version="Gitaly, version , built "
Nov 13 02:55:16 davinci gitaly[19881]: time="2017-11-13T02:55:16Z" level=warning msg="git path not configured. Using default path resolution" resolvedPath=/nix/store/20fcgg1pac9ygpcswh6g3mc62cqv0nj1-git-2.15.0/bin/git
Nov 13 02:55:16 davinci gitaly[19881]: time="2017-11-13T02:55:16Z" level=fatal msg="load config" config_path=/nix/store/bzh87nyydaw9kl6a0g1riwzpccypslja-gitaly.toml error="open Warning: the running version of Bundler (1.14.6) is older than the version that created the lockfile (1.15.4). We suggest you upgrade to the latest version of Bundler by running `gem install bundler`.\n/nix/store/x935b8k731a5sy58gymsdwnay53cdipb-gitaly-env/lib/ruby/gems/2.3.0/gems/github-linguist-4.7.6/lib/linguist/languages.json: no such file or directory"
Nov 13 02:55:16 davinci systemd[1]: gitaly.service: Main process exited, code=exited, status=1/FAILURE
Nov 13 02:55:16 davinci systemd[1]: gitaly.service: Unit entered failed state.
Nov 13 02:55:16 davinci systemd[1]: gitaly.service: Failed with result 'exit-code'.
Nov 13 02:55:17 davinci systemd[1]: gitaly.service: Service hold-off time over, scheduling restart.
Nov 13 02:55:17 davinci systemd[1]: Stopped gitaly.service.