On an Ubuntu 16.04 machine with the php7.0 package installed, spelling correction errors out with:
arc dieff [2016-09-29 18:59:12] EXCEPTION: (Error) Call to undefined function utf8_decode() at [<phutil>/src/utils/utf8.php:236] arcanist(head=master, ref.master=89e8b4852384), dblib(head=bin, ref.master=a6f1cdafe4af, ref.bin=1537c1180274), phutil(head=master, ref.master=9c03af69571f) #0 phutil_utf8_strlen(string) called at [<phutil>/src/parser/argument/PhutilArgumentSpellingCorrector.php:120] #1 PhutilArgumentSpellingCorrector::correctSpelling(string, array) called at [<arcanist>/src/configuration/ArcanistConfiguration.php:148] #2 ArcanistConfiguration::selectWorkflow(string, array, ArcanistConfigurationManager, PhutilConsole) called at [<arcanist>/scripts/arcanist.php:193]
This is because the php7.0 package does not install the XML extension, which is what provides utf8_decode. Installing the php7.0-xml package provides the extension and fixes the error, but it would be good to either message this better, or have a workaround for such installs (which are likely commonplace).