Confirm correct handling of out-of-scope file access

[acdha]

We should have invalid bags testing the warnings about out-of-scope file paths:

https://tools.ietf.org/html/draft-kunze-bagit-14#section-6.1

This should include tests for a leading /, ../, ~<username>/, C:\, and \\?\ and \\.\.

[acdha]

Before closing this issue we should make sure we have fetch.txt counterparts for all of these checks

[johnscancella]

@acdha are we missing anything from this? Should we go ahead and close?

[acdha]

👍