jonkemp/gulp-useref — pull request #51 by coderhaoxin (2014-08-29 02:41:56+00:00)
Title: more clear error message when file not exist

when the file is not exist.
the error msg is
```
events.js:87
throw Error('Uncaught, unspecified "error" event.');
^
Error: Uncaught, unspecified "error" event.
at Error (native)
at Transform.EventEmitter.emit (events.js:87:13)
```
it's hard to read.

after this change, the message is
```
events.js:85
throw er; // Unhandled 'error' event
^
Error: ENOENT, no such file or directory '...'

```