Broken gulp build still returns error code 0

[crittermike]

Here's some example output from my project:

5.65s$ gulp build --production

[16:14:55] Requiring external module babel-core/register

[16:14:56] Using gulpfile ~/build/mikecrittenden/shortkeys/gulpfile.babel.js

[16:14:56] Starting 'build'...

[16:14:56] Starting 'clean'...

[16:14:56] Finished 'clean' after 4.13 ms

[16:14:56] Starting 'vendor:mousetrap'...

[16:14:56] Starting 'vendor:bootstrap'...

[16:14:56] Starting 'vendor:codemirror'...

[16:14:56] Starting 'vendor:angular'...

[16:14:56] Starting 'vendor:keyscss'...

[16:14:56] Starting 'manifest'...

[16:14:56] Starting 'scripts'...

[16:14:56] Starting 'styles:css'...

[16:14:56] Starting 'styles:less'...

[16:14:56] Starting 'styles:sass'...

[16:14:56] Starting 'pages'...

[16:14:56] Starting 'locales'...

[16:14:56] Starting 'images'...

[16:14:56] Starting 'fonts'...

[16:14:56] Starting 'chromereload'...

[16:14:56] Finished 'chromereload' after 151 μs

[16:14:56] Finished 'styles:css' after 23 ms

[16:14:56] Finished 'styles:less' after 21 ms

[16:14:56] Finished 'fonts' after 18 ms

[16:14:57] Finished 'pages' after 279 ms

[16:14:57] Finished 'manifest' after 333 ms

[16:14:57] Finished 'styles:sass' after 286 ms

[16:14:57] Starting 'styles'...

[16:14:57] Finished 'styles' after 30 μs

[16:14:57] Finished 'locales' after 285 ms

[16:14:57] Finished 'vendor:mousetrap' after 364 ms

[16:14:57] Finished 'vendor:bootstrap' after 360 ms

[16:14:57] Finished 'vendor:codemirror' after 358 ms

[16:14:57] Finished 'vendor:angular' after 358 ms

[16:14:57] Finished 'vendor:keyscss' after 357 ms

[16:14:57] Starting 'vendor'...

[16:14:57] Finished 'vendor' after 6.41 μs

[16:14:57] gulp-imagemin: Minified 4 images (saved 5.11 kB - 48.4%)

[16:14:57] Finished 'images' after 700 ms

[16:15:00] Finished 'scripts' Hash: 21b542b739c502552262

Version: webpack 3.10.0

Time: 2806ms

           Asset     Size  Chunks             Chunk Names

      options.js   136 kB       0  [emitted]  options

contentscript.js  1.53 kB       1  [emitted]  contentscript

   background.js  6.76 kB       2  [emitted]  background

   [0] multi ./app/scripts/background.js 28 bytes {2} [built]

   [1] ./app/scripts/background.js 10.8 kB {2} [built]

   [2] multi ./app/scripts/contentscript.js 28 bytes {1} [built]

   [3] ./app/scripts/contentscript.js 3.58 kB {1} [built]

   [4] multi ./app/scripts/options.js 28 bytes {0} [built]

   [5] ./app/scripts/options.js 10.7 kB {0} [built]

   [6] ./node_modules/angular-ui-bootstrap/index.js 71 bytes {0} [built]

   [7] ./node_modules/angular-ui-bootstrap/dist/ui-bootstrap-tpls.js 277 kB {0} [built]

   [8] ./node_modules/angular-ui-codemirror/src/ui-codemirror.js 4.52 kB {0} [built]


ERROR in ./app/scripts/options.js

Module not found: Error: Can't resolve 'Angular' in '/home/travis/build/mikecrittenden/shortkeys/app/scripts'

 @ ./app/scripts/options.js 5:15-33

 @ multi ./app/scripts/options.js


ERROR in ./app/scripts/options.js

Module not found: Error: Can't resolve 'CodeMirror' in '/home/travis/build/mikecrittenden/shortkeys/app/scripts'

 @ ./app/scripts/options.js 9:18-39

 @ multi ./app/scripts/options.js


ERROR in ./app/scripts/options.js

Module not found: Error: Can't resolve 'CodeMirror/addon/edit/closebrackets.js' in '/home/travis/build/mikecrittenden/shortkeys/app/scripts'

 @ ./app/scripts/options.js 15:0-49

 @ multi ./app/scripts/options.js


ERROR in ./app/scripts/options.js

Module not found: Error: Can't resolve 'CodeMirror/addon/edit/matchbrackets.js' in '/home/travis/build/mikecrittenden/shortkeys/app/scripts'

 @ ./app/scripts/options.js 17:0-49

 @ multi ./app/scripts/options.js


ERROR in ./app/scripts/options.js

Module not found: Error: Can't resolve 'CodeMirror/mode/javascript/javascript.js' in '/home/travis/build/mikecrittenden/shortkeys/app/scripts'

 @ ./app/scripts/options.js 13:0-51

 @ multi ./app/scripts/options.js

[16:15:00] Finished 'scripts' after 3.13 s

[16:15:00] Finished 'build' after 3.15 s



The command "gulp build --production" exited with 0.


Done. Your build exited with 0.

Note that there are multiple Module not found errors, but the command still returns a success code. How can I make this return an error code instead?