Seems this issue has reappeared in bundler 1.14.x in combination with 2.4.x rubygems. See:
Its not an issue with either rubygems 2.6.x (2.6.6 in one env.), or with bundler 1.13.7 as I'm able to demonstrate here:
I think this is very similar to reports and PR #4981.
If the rake project can reproduce the issue, we don't know via travis, given that its pegged to bundler 1.13.x:
But here are some other reports of this with bundler 1.14.3:
We really need a test case that reproduces this, since I can't reproduce it on any of the ruby apps I have lying around
Experiencing the same issue on a rails app using rubygems 2.4.8 and bundler 1.14.3
I have just updated my rubygems to 2.6.10 and the issue is gone fyi.