~/src/phacility/core (master) $ ./bin/host download --file F5518806 --save-as ./foo
[2018-04-11 17:53:50] EXCEPTION: (PhutilMissingSymbolException) Failed to load class or interface 'PhabricatorEnv': the class or interface 'PhabricatorEnv' is not defined in the library map for any loaded phutil library.

If you are not a developer, this almost always means that a library is out of date. For example, you may have upgraded `phabricator` without upgrading `libphutil`, or vice versa. It might also mean that you need to restart Apache or PHP-FPM. Make sure all libraries are up to date and all services have been restarted.

If you are a developer and this symbol was recently added or moved, your library map may need to be rebuilt. You can rebuild the map by running 'arc liberate'. For more information, see:

https://secure.phabricator.com/book/phabcontrib/article/adding_new_classes/ at [<phutil>/src/__phutil_library_init__.php:25]
libcore(), phutil(head=master, ref.master=02012dae43a5)
  #0 __phutil_autoload(string)
  #1 spl_autoload_call(string) called at [<libcore>/workflow/base/CoreWorkflow.php:467]
  #2 CoreWorkflow::newConduitClient() called at [<libcore>/workflow/base/CoreWorkflow.php:503]
  #3 CoreWorkflow::readAllConduitResults(string, array) called at [<libcore>/workflow/base/CoreWorkflow.php:489]
  #4 CoreWorkflow::readOneConduitResult(string, array) called at [<libcore>/workflow/host/CoreHostDownloadWorkflow.php:92]
  #5 CoreHostDownloadWorkflow::execute(PhutilArgumentParser) called at [<phutil>/src/parser/argument/PhutilArgumentParser.php:441]
  #6 PhutilArgumentParser::parseWorkflowsFull(array) called at [<phutil>/src/parser/argument/PhutilArgumentParser.php:333]
  #7 PhutilArgumentParser::parseWorkflows(array) called at [/Users/amckinley/src/phacility/core/scripts/host.php:19]