Steps to reproduce:

1. Create otherwise valid yaml file, but instead of spaces use tabs.
2. See error when loading with require:

YAMLException: JS-YAML: the stream contains non-printable characters in "/home/developer/code/request-tester/app.yml" at line 1, column 1

What should appear:

1. Either error at appearance of first invalid character (tab)
2. or general error that there are tabs in the file

I should have some time this weekend to do the pull request here.