sudo apt-get install erlang-xmerl can solve following exception while starting phoenix.server.
=INFO REPORT==== 18-Jan-2016::15:45:50 ===
application: logger
exited: stopped
type: temporary
** (Mix) Could not start application xmerl: could not find application file: xmerl.app
I started getting this exception right after I added :floki in applications: under mix.exs.