error in building dist file when running 'npm run build:browser'

[southeastcon2017]

ERROR in ./tests/testrunner.js
Module not found: Error: Can't resolve './reftests' in '/Users/...'
@ ./tests/testrunner.js 9:16-37
npm ERR! code ELIFECYCLE
npm ERR! errno 2
npm ERR! html2canvas@1.0.0-alpha.1 build:browser: webpack
npm ERR! Exit status 2
npm ERR!
npm ERR! Failed at the html2canvas@1.0.0-alpha.1 build:browser script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:

[niklasvh]

Run npm run build