Let CLI know when procs die.

lib/util/procutil.js

@@ -0,0 +1,36 @@
+var util = require('util')
+var cp = require('child_process')
+
+var Promise = require('bluebird')
+
+function ExitError(code) {
+  Error.call(this, util.format('Exit code "%d"', code))
+  this.name = 'ExitError'
+  this.code = code
+  Error.captureStackTrace(this, ExitError)
+}
+
+util.inherits(ExitError, Error)
+
+// Export
+module.exports.ExitError = ExitError
+
+// Export
+module.exports.fork = function() {
+  var args = arguments
+
+  return new Promise(function(resolve, reject) {
+    var proc = cp.fork.apply(cp, args)
+
+    proc.on('error', function(err) {
+      reject(err)
+      proc.kill()
+    })
+
+    proc.on('exit', function(code) {
+      if (code > 0) {
+        reject(new ExitError(code))
+      }
+    })
+  })
+}