hermes-engine installation via CocoaPods seems to be related to an issue with the CocoaPods cache or the hermes-engine pod itself. Specifically, the error Errno::EEXIST - File exists @ syserr_fail2_in suggests that there is a conflict or issue with existing files in your CocoaPods cache or the directory structure where the hermes-engine is being installed.
TO FIX IT:
Sounds like this is an issue with CocoaPods 1.15.0. Fixed it by installing version 1.14.3 of CocoaPods.
sudo gem uninstall cocoapods
sudo gem install cocoapods -v 1.14.3
pod --version
rm -rf Pods
rm Podfile.lock
pod install
This has actually been fixed in CocoaPods version 1.15.2. So there is no longer a need to fix this by downgrading as mentioned above. Just update to the latest version.
hermes-engine installation via CocoaPods seems to be related to an issue with the CocoaPods cache or the hermes-engine pod itself. Specifically, the error Errno::EEXIST - File exists @ syserr_fail2_in suggests that there is a conflict or issue with existing files in your CocoaPods cache or the directory structure where the hermes-engine is being installed.
TO FIX IT: Sounds like this is an issue with CocoaPods 1.15.0. Fixed it by installing version 1.14.3 of CocoaPods.
https://forums.developer.apple.com/forums/thread/745518