According to OTP naming conventions (see http://erlang.org/doc/design_principles/applications.html#directory-structure), the application resource file is supposed to be src/${application}.app.src, but for elvis_core this file is called src/elvis.app.src. Also, the file contents specifies the application name to be "elvis" instead of "elvis_core".

  application, elvis,
  [
   {pkg_name, elvis_core},
...

This means that we cannot start the elvis_core application as documented by doing application:start(elvis_core).:

===> Verifying dependencies...
===> Compiling elvis
Erlang/OTP 19 Klarna-g270c04d412 [erts-8.3.5.4] [source-270c04d412] [64-bit] [smp:4:4] [async-threads:1] [hipe] [kernel-poll:false]

Eshell V8.3.5.4  (abort with ^G)
1> application:start(elvis_core).
{error,{"no such file or directory","elvis_core.app"}}
2>