Upgade to more recent version of lager.

[edwardttril]

The latest is 3.1.0.

Time to upgrade to at least 3.x?

https://github.com/basho/lager/tree/3.1.0

[Steve Cohen]

These deps are locked due to elixometer's deps.

[Jon Parise]

This was addressed a while back. We're now using lager >= 3.2.1 in the master branch.