'Bad option: esversion' but not using esversion?

[gnh1201]

I want solve 'Bad option: esversion' error, but I am not using esversion in source code. anything.

grep -Hrn "esversion" -> Nothing. ( find all files contains 'esversion', result is nothing. )

Why occurred this error?

Error console:

[15:49:47] Using gulpfile ~/testpack/gulpfile.js
[15:49:47] Starting 'less'...
[15:49:47] Finished 'less' after 9.63 ms
[15:49:47] Starting 'templates'...
[15:49:47] Finished 'templates' after 12 ms
[15:49:47] Starting 'compile:dev'...
/home/user/testpack/src/testpack/core/emitter.js: line 0, col 0, Bad option: 'esversion'.

1 error
/home/user/testpack/src/testpack/core/promise.js: line 0, col 0, Bad option: 'esversion'.

1 error
/home/user/testpack/src/testpack/core/view.js: line 0, col 0, Bad option: 'esversion'.

1 error
/home/user/testpack/src/testpack/wm/window.js: line 0, col 0, Bad option: 'esversion'.

1 error
/home/user/testpack/src/testpack/wm/windowmanager.js: line 0, col 0, Bad option: 'esversion'.

1 error
/home/user/testpack/src/testpack/wm/modes/default.js: line 0, col 0, Bad option: 'esversion'.

1 error
/home/user/testpack/src/testpack/wm/modes/expose.js: line 0, col 0, Bad option: 'esversion'.

1 error
/home/user/testpack/src/testpack/wm/modes/fullscreen.js: line 0, col 0, Bad option: 'esversion'.

1 error
/home/user/testpack/src/main.js: line 0, col 0, Bad option: 'esversion'.

1 error
/home/user/testpack/src/testpack.js: line 0, col 0, Bad option: 'esversion'.

1 error
[15:49:48] Finished 'compile:dev' after 595 ms
[15:49:48] Starting 'compile:prod'...
[15:49:49] Finished 'compile:prod' after 812 ms
[15:49:49] Starting 'compile'...
[15:49:49] Finished 'compile' after 1.63 μs
[15:49:49] Starting 'default'...
[15:49:49] Finished 'default' after 1.94 μs

[jugglinmike]

Hi there! We'd like to help out, but we'll need some more information first. From the project's contribution guidelines:

If you believe you have identified incorrect behavior, please let the team know
by filing an issue. In order to help the team diagnose and fix the problem, the
issue report should have the following information:

• Version of JSHint being used
• Input source code (simplified to only contain details necessary to
  demonstrate the problem)
• Configuration values
• Description of expected behavior
• Description of actual behavior

Could you get back to us with this information?