add istanbul ignore for the benefit of node 8

Author: isaacs

lib/util/spawn.js

@@ -5,7 +5,9 @@ module.exports = (cmd, args, options, ermsg) => new Promise((res, rej) => {
   const proc = spawn(cmd, args, options)
   const stdout = []
   const stderr = []
-  proc.on('error', er => withStdio(rej, er, stdout, stderr))
+  proc.on('error',
+    /* istanbul ignore next: node 8 just throws from spawn() */
+    er => withStdio(rej, er, stdout, stderr))
   if (proc.stdout) {
     proc.stdout.on('data', c => stdout.push(c))
     proc.stdout.on('error', er => withStdio(rej, er, stdout, stderr))