Heroku: Exit code should not be zero if there is an error applying patches

[OliverJAsh]

When yarn is ran as part of a build for a Heroku application and the patches fail to apply, the exit code is 0. I expect it to be non-zero.

This means that a Heroku application will be deployed even if the patches failed to apply (!!).

This is happening because Heroku is not detected by the is-ci check.

Related: #143

[ds300]

Thanks for pointing this out!! This exit code business is such a minefield. Would adding a NODE_ENV=production check take care of it?

[OliverJAsh]

Would adding a NODE_ENV=production check take care of it?

In our case, yes, but some users might deploy to Heroku with NODE_ENV=staging 🤔