New update-checker breaks compatibility with Read Only filesystems

[tomgco]

The Pull Request: #347 has introduced a new update checking module. This module tries to create a temporary folder and file under /tmp - /tmp/update-check/serve-latest.json.

However in our deployments, as our file-systems are Read Only the new update breaks. The previous point release 6.5.3 was compatible and working with our setup, whereas 6.5.4 has broken this compatibility.

Operating System: Alpine Linux
Node: 8.11.1

A stack trace can be found below:

(node:6) UnhandledPromiseRejectionWarning: Error: EROFS: read-only file system, mkdir '/tmp/update-check'
(node:6) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:6) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
(node:6) UnhandledPromiseRejectionWarning: Error: ENOENT: no such file or directory, open '/tmp/update-check/serve-latest.json'
(node:6) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 2)

[GlenTiki]

Notice for anyone else who ends up here: you're probably trying to run serve in a production env. If you set the NODE_ENV env variable to be production, this issue should go away ✨

[leo]

Fixed in the latest release! 😊