mitchellh/vagrant — pull request #1928 by korya (2013-07-15 06:02:31+00:00)
Title: When top-of-branch vagrant tries to execute a command, which does not exist in PATH, error report does not display the executable name.

In failure case at line lib/vagrant/util/subprocess.rb:30 command[0] is set to nil. But you still need to display the executable name.

The simplest solution: store the executable name in a temp variable, and display it in a failure case.