Github user Leemoonsoo commented on the issue:
https://github.com/apache/zeppelin/pull/2135
The error
```
[ERROR] error An unexpected error occurred:
"https://registry.yarnpkg.com/binary-extensions/-/binary-extensions-1.8.0.tgz:
Request failed \"502 Bad Gateway\"".
[ERROR] Failed to execute goal
com.github.eirslett:frontend-maven-plugin:1.3:yarn (yarn install) on project
zeppelin-web: Failed to run task: 'yarn install --no-lockfile' failed. (error
code 1) -> [Help 1]
[ERROR]
```
looks like temporary network problem. You can always restart [the failed
Job](https://travis-ci.org/dlukyanov/zeppelin/jobs/211224371) and see if it
passing.
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