title: Traceback when building an exrm release of a Phoenix app
body: <p>After SCP-ing my Phoenix app dir from my Macbook to my Fedora VM, I try to build a production exrm release but an exception is raised:</p>
  
  <pre><code>==&gt; Building release with MIX_ENV=prod.
  ==&gt; Generating relx configuration...
  ==&gt; Generating sys.config...
  ==&gt; Generating boot script...
  ==&gt; Performing protocol consolidation...
  ==&gt; Conform: Loading schema...
  ==&gt; Conform: No schema found, conform will not be packaged in this release!
  ==&gt; Generating release...
  ===&gt; Missing beam file megaco_flex_scanner &lt;&lt;"/usr/lib64/erlang/lib/megaco-3.17.3/ebin/megaco_flex_scanner.beam"&gt;&gt;
  ===&gt; Missing beam file 'Elixir.Access' &lt;&lt;"/home/me/lartbot/rel/lartbot/lib/elixir-1.1.1/ebin/Elixir.Access.beam"&gt;&gt;
  ===&gt; Missing beam file error_handler &lt;&lt;"/home/me/lartbot/rel/lartbot/lib/kernel-4.1/ebin/error_handler.beam"&gt;&gt;
  ===&gt; Missing beam file erl_anno &lt;&lt;"/home/me/lartbot/rel/lartbot/lib/stdlib-2.6/ebin/erl_anno.beam"&gt;&gt;
  ===&gt; Missing beam file cow_cookie &lt;&lt;"/home/me/lartbot/rel/lartbot/lib/cowlib-1.0.2/ebin/cow_cookie.beam"&gt;&gt;
  ===&gt; Missing beam file cowboy_middleware &lt;&lt;"/home/me/lartbot/rel/lartbot/lib/cowboy-1.0.4/ebin/cowboy_middleware.beam"&gt;&gt;
  ===&gt; Missing beam file 'Elixir.Phoenix.HTML' &lt;&lt;"/home/me/lartbot/rel/lartbot/lib/phoenix_html-2.3.0/ebin/Elixir.Phoenix.HTML.beam"&gt;&gt;
  ===&gt; Missing beam file 'Elixir.Poison' &lt;&lt;"/home/me/lartbot/rel/lartbot/lib/poison-1.5.0/ebin/Elixir.Poison.beam"&gt;&gt;
  ===&gt; Missing beam file 'Elixir.Plug' &lt;&lt;"/home/me/lartbot/rel/lartbot/lib/plug-1.0.3/ebin/Elixir.Plug.beam"&gt;&gt;
  ===&gt; Missing beam file 'Elixir.Mix.Phoenix' &lt;&lt;"/home/me/lartbot/rel/lartbot/lib/phoenix-1.0.4/ebin/Elixir.Mix.Phoenix.beam"&gt;&gt;
  
  02:59:36.683 [error] Error in process &lt;0.10938.0&gt; with exit value: {{badmatch,{error,enoent}},[{rlx_prv_assembler,rewrite_app_file,2,[{file,"src/rlx_prv_assembler.erl"},{line,215}]},{lists,map,2,[{file,"lists.erl"},{line,1237}]},{ec_plists,'-local_runmany/3-fun-0-',3,[{file,"src/ec_plists.erl"},... 
  
  
  ** (exit) an exception was raised:
      ** (MatchError) no match of right hand side value: {:error, :enoent}
          src/rlx_prv_assembler.erl:215: :rlx_prv_assembler.rewrite_app_file/2
          (stdlib) lists.erl:1237: :lists.map/2
          src/ec_plists.erl:753: anonymous fn/3 in :ec_plists.local_runmany/3
      src/ec_plists.erl:900: :ec_plists.handle_error/3
      src/ec_plists.erl:764: :ec_plists.local_runmany/3
      src/rlx_prv_assembler.erl:152: :rlx_prv_assembler.copy_app_directories_to_output/3
      src/rlx_prv_assembler.erl:58: :rlx_prv_assembler.do/1
      src/relx.erl:286: :relx.run_provider/2
      (stdlib) lists.erl:1261: :lists.foldl/3
      src/relx.erl:266: :relx.run_providers/1
      lib/exrm/utils.ex:94: ReleaseManager.Utils.relx/5
  </code></pre>
  
  <p>I'm completely new to Erlang, Elixir, and Phoenix so I haven't really got the faintest idea how to troubleshoot this one.</p>