title: Elixir Wallaby crashes on mix test
body: <p>I am trying to incorporate Wallaby into my phoenix app. I have followed the setup guide closely and made sure that phantomjs is properly installed, however on mix test I get the following error:</p>
  
  <pre><code>** (MatchError) no match of right hand side value:
  </code></pre>
  
  <p>My operating system is Windows10.
  Elixir version: 1.10.1
  Phoenix version: 1.4.15
  Wallaby version: 0.23.0
  Phantomjs version: 2.1.1
  Here is the full output:</p>
  
  <pre><code>mix test
  
  06:21:54.255 [info]  Already up
  06:21:55.380 [error] Task #PID&lt;0.486.0&gt; started from #PID&lt;0.488.0&gt; terminating
  ** (stop) :eacces
      erlang.erl:2213: :erlang.open_port({:spawn_executable, 'C:\\Users\\SARELV~1\\AppData\\Local\\Temp/kz9cgp/wrapper'}, [:binary, :stream, :use_stdio, :exit_status, :stderr_to_stdout, {:args, ["phantomjs", "--webdriver=55182", "--local-storage-path=C:\\Users\\SARELV~1\\AppData\\Local\\Temp/kz9cgp/local_storage"]}])
      (wallaby 0.23.0) lib/wallaby/phantom/server/start_task.ex:85: Wallaby.Phantom.Server.StartTask.start_phantom/1
      (wallaby 0.23.0) lib/wallaby/phantom/server/start_task.ex:28: Wallaby.Phantom.Server.StartTask.run/2
      (elixir 1.10.1) lib/task/supervised.ex:90: Task.Supervised.invoke_mfa/2
      (elixir 1.10.1) lib/task/supervised.ex:35: Task.Supervised.reply/5
      (stdlib 3.8) proc_lib.erl:249: :proc_lib.init_p_do_apply/3
  Function: &amp;Wallaby.Phantom.Server.StartTask.run/2
      Args: [#PID&lt;0.486.0&gt;, %Wallaby.Phantom.Server.ServerState{phantom_args: [], phantom_os_pid: nil, phantom_path: "phantomjs", port_number: 55182, workspace_path: "C:\\Users\\SARELV~1\\AppData\\Local\\Temp/kz9cgp", wrapper_script_os_pid: nil, wrapper_script_port: nil}]
  ** (MatchError) no match of right hand side value: {:error, {:wallaby, {{:shutdown, {:failed_to_start_child, Wallaby.Phantom, {:shutdown, {:failed_to_start_child, Wallaby.ServerPool, {{:badmatch, {:error, {:eacces, [{:erlang, :open_port, [{:spawn_executable, 'C:\\Users\\SARELV~1\\AppData\\Local\\Temp/kz9cgp/wrapper'}, [:binary, :stream, :use_stdio, :exit_status, :stderr_to_stdout, {:args, ["phantomjs", "--webdriver=55182", "--local-storage-path=C:\\Users\\SARELV~1\\AppData\\Local\\Temp/kz9cgp/local_storage"]}]], [file: 'erlang.erl', line: 2213]}, {Wallaby.Phantom.Server.StartTask, :start_phantom, 1, [file: 'lib/wallaby/phantom/server/start_task.ex', line: 85]}, {Wallaby.Phantom.Server.StartTask, :run, 2, [file: 'lib/wallaby/phantom/server/start_task.ex', line: 28]}, {Task.Supervised, :invoke_mfa, 2, [file: 'lib/task/supervised.ex', line: 90]}, {Task.Supervised, :reply, 5, [file: 'lib/task/supervised.ex', line: 35]}, {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 249]}]}}}, [{:poolboy, :new_worker, 1, [file: 'c:/Coding/Projects/BoomhuisOnline/boomhuis/deps/poolboy/src/poolboy.erl', line: 283]}, {:poolboy, :prepopulate, 3, [file: 'c:/Coding/Projects/BoomhuisOnline/boomhuis/deps/poolboy/src/poolboy.erl', line: 304]}, {:poolboy, :init, 3, [file: 'c:/Coding/Projects/BoomhuisOnline/boomhuis/deps/poolboy/src/poolboy.erl', line: 153]}, {:gen_server, :init_it, 2, [file: 'gen_server.erl', line: 374]}, {:gen_server, :init_it, 6, [file: 'gen_server.erl', line: 342]}, {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 249]}]}}}}}, {Wallaby, :start, [:normal, []]}}}}
      test/test_helper.exs:5: (file)
      (elixir 1.10.1) lib/code.ex:917: Code.require_file/2
      (elixir 1.10.1) lib/enum.ex:783: Enum."-each/2-lists^foreach/1-0-"/2
      (elixir 1.10.1) lib/enum.ex:783: Enum.each/2
  06:21:55.392 [error] GenServer #PID&lt;0.485.0&gt; terminating
  ** (MatchError) no match of right hand side value: {:error, {:eacces, [{:erlang, :open_port, [{:spawn_executable, 'C:\\Users\\SARELV~1\\AppData\\Local\\Temp/kz9cgp/wrapper'}, [:binary, :stream, :use_stdio, :exit_status, :stderr_to_stdout, {:args, ["phantomjs", "--webdriver=55182", "--local-storage-path=C:\\Users\\SARELV~1\\AppData\\Local\\Temp/kz9cgp/local_storage"]}]], [file: 'erlang.erl', line: 2213]}, {Wallaby.Phantom.Server.StartTask, :start_phantom, 1, [file: 'lib/wallaby/phantom/server/start_task.ex', line: 85]}, {Wallaby.Phantom.Server.StartTask, :run, 2, [file: 'lib/wallaby/phantom/server/start_task.ex', line: 28]}, {Task.Supervised, :invoke_mfa, 2, [file: 'lib/task/supervised.ex', line: 90]}, {Task.Supervised, :reply, 5, [file: 'lib/task/supervised.ex', line: 35]}, {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 249]}]}}
      (poolboy 1.5.2) c:/Coding/Projects/BoomhuisOnline/boomhuis/deps/poolboy/src/poolboy.erl:283: :poolboy.new_worker/1
      (poolboy 1.5.2) c:/Coding/Projects/BoomhuisOnline/boomhuis/deps/poolboy/src/poolboy.erl:304: :poolboy.prepopulate/3
      (poolboy 1.5.2) c:/Coding/Projects/BoomhuisOnline/boomhuis/deps/poolboy/src/poolboy.erl:153: :poolboy.init/3
      (stdlib 3.8) gen_server.erl:374: :gen_server.init_it/2
      (stdlib 3.8) gen_server.erl:342: :gen_server.init_it/6
      (stdlib 3.8) proc_lib.erl:249: :proc_lib.init_p_do_apply/3
  Last message: {:EXIT, #PID&lt;0.484.0&gt;, {{:badmatch, {:error, {:eacces, [{:erlang, :open_port, [{:spawn_executable, 'C:\\Users\\SARELV~1\\AppData\\Local\\Temp/kz9cgp/wrapper'}, [:binary, :stream, :use_stdio, :exit_status, :stderr_to_stdout, {:args, ["phantomjs", "--webdriver=55182", "--local-storage-path=C:\\Users\\SARELV~1\\AppData\\Local\\Temp/kz9cgp/local_storage"]}]], [file: 'erlang.erl', line: 2213]}, {Wallaby.Phantom.Server.StartTask, :start_phantom, 1, [file: 'lib/wallaby/phantom/server/start_task.ex', line: 85]}, {Wallaby.Phantom.Server.StartTask, :run, 2, [file: 'lib/wallaby/phantom/server/start_task.ex', line: 28]}, {Task.Supervised, :invoke_mfa, 2, [file: 'lib/task/supervised.ex', line: 90]}, {Task.Supervised, :reply, 5, [file: 'lib/task/supervised.ex', line: 35]}, {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 249]}]}}}, [{:poolboy, :new_worker, 1, [file: 'c:/Coding/Projects/BoomhuisOnline/boomhuis/deps/poolboy/src/poolboy.erl', line: 283]}, {:poolboy, :prepopulate, 3, [file: 'c:/Coding/Projects/BoomhuisOnline/boomhuis/deps/poolboy/src/poolboy.erl', line: 304]}, {:poolboy, :init, 3, [file: 'c:/Coding/Projects/BoomhuisOnline/boomhuis/deps/poolboy/src/poolboy.erl', line: 153]}, {:gen_server, :init_it, 2, [file: 'gen_server.erl', line: 374]}, {:gen_server, :init_it, 6, [file: 'gen_server.erl', line: 342]}, {:proc_lib, :init_p_do_apply, 3, [file: 'proc_lib.erl', line: 249]}]}}
  </code></pre>
  
  <p>Any help/advice will be greatly appreciated!</p>