Sourcemap build errors

[robertknight]

Steps to reproduce

1. Set the NODE_ENV env var to production
2. Run gulp build-js

Results

Output: Includes a ton of unexpected warnings:

 ~/h/r/h > set -x NODE_ENV production
 ~/h/r/h > gulp build-js
[08:26:43] Using gulpfile ~/hypothesis/repos/h/gulpfile.js
[08:26:43] Starting 'build-vendor-js'...
[08:26:49] Finished 'build-vendor-js' after 5.88 s
[08:26:49] Starting 'build-js'...
WARN: Couldn't figure out mapping for ?:11,0 → 1,549 []
WARN: Couldn't figure out mapping for ?:11,4 → 1,552 []
WARN: Couldn't figure out mapping for ?:11,32 → 1,561 []
WARN: Couldn't figure out mapping for ?:11,21 → 1,579 []
WARN: Couldn't figure out mapping for ?:11,73 → 1,588 []
WARN: Couldn't figure out mapping for ?:11,53 → 1,604 []
WARN: Couldn't figure out mapping for ?:11,60 → 1,612 []
WARN: Couldn't figure out mapping for ?:11,84 → 1,621 []
WARN: Couldn't figure out mapping for ?:11,94 → 1,630 []

Notes

This may relate to hughsk/uglifyify#56

[leedenison]

Obsolete.