cowboy compilation output

$ mix deps.compile
==> fs (compile)
==> ranch (compile)
==> poolboy (compile)
==> cowlib (compile)
Uncaught error in rebar_core: {'EXIT',
                               {{badmatch,{error,eexist}},
                                [{rebar_deps,update_deps_code_path,2,[]},
                                 {rebar_deps,preprocess,2,[]},
                                 {rebar_core,acc_modules,5,[]},
                                 {rebar_core,process_dir1,7,[]},
                                 {rebar_core,process_commands,2,[]},
                                 {rebar,main,1,[]},
                                 {escript,run,2,
                                  [{file,"escript.erl"},{line,752}]},
                                 {escript,start,1,
                                  [{file,"escript.erl"},{line,276}]}]}}
** (Mix) Could not compile dependency :cowboy, "/home/certainty/.mix/rebar" command failed. You can recompile this dependency with "mix deps.compile cowboy", update it with "mix deps.update cowboy" or clean it with "mix deps.clean cowboy"

environment

Mix 1.1.1
Elixir 1.1.1
Erlang/OTP 17 [erts-6.1] [source] [64-bit] [smp:4:4] [async-threads:10] [hipe] [kernel-poll:false]

mix.lock

%{"cowboy": {:hex, :cowboy, "1.0.3"},
  "cowlib": {:hex, :cowlib, "1.0.1"},
  "decimal": {:hex, :decimal, "1.1.0"},
  "ecto": {:hex, :ecto, "1.0.4"},
  "fs": {:hex, :fs, "0.9.2"},
  "phoenix": {:hex, :phoenix, "1.0.3"},
  "phoenix_ecto": {:hex, :phoenix_ecto, "1.2.0"},
  "phoenix_html": {:hex, :phoenix_html, "2.2.0"},
  "phoenix_live_reload": {:hex, :phoenix_live_reload, "1.0.1"},
  "plug": {:hex, :plug, "1.0.2"},
  "poison": {:hex, :poison, "1.5.0"},
  "poolboy": {:hex, :poolboy, "1.5.1"},
  "postgrex": {:hex, :postgrex, "0.9.1"},
  "ranch": {:hex, :ranch, "1.1.0"}}