React native error: Error: watch EMFILE

I ran into the same issue updating to macOS Sierra, however, it turned out that watchman was to blame. Looking through the logs I stumbled upon numerous odd permission issues.

As covered on github/facebook/react-native#9943, reinstalling watchman solves the issue.

rm -rf /usr/local/var/run/watchman/
brew uninstall watchman
brew install watchman