I just installed fsevents-watcher on my MacOS 10.13.6 (High Sierra). It seems to work, but it gives some MacOS warnings. Other people have seen the same warnings (http://sd.jtimothyking.com/2018/07/26/stub-file-and-library-file-out-of-sync/) but their suggestion didn't help me (I'm already on the latest command line tools).

$ ./launch.sh

_/Users/asdf/GitHub/fsevents-watcher

ld: warning: text-based stub file /System/Library/Frameworks//CoreServices.framework/CoreServices.tbd and library file /System/Library/Frameworks//CoreServices.framework/CoreServices are out of sync. Falling back to library file for linking.
ld: warning: text-based stub file /System/Library/Frameworks//CFNetwork.framework/Versions/A/CFNetwork.tbd and library file /System/Library/Frameworks//CFNetwork.framework/Versions/A/CFNetwork are out of sync. Falling back to library file for linking.
ld: warning: text-based stub file /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/OSServices.framework/Versions/A/OSServices.tbd and library file /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/OSServices.framework/Versions/A/OSServices are out of sync. Falling back to library file for linking.
ld: warning: text-based stub file /System/Library/Frameworks//CoreFoundation.framework/Versions/A/CoreFoundation.tbd and library file /System/Library/Frameworks//CoreFoundation.framework/Versions/A/CoreFoundation are out of sync. Falling back to library file for linking.
ld: warning: text-based stub file /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/LaunchServices.tbd and library file /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/LaunchServices are out of sync. Falling back to library file for linking.
ld: warning: text-based stub file /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/SharedFileList.framework/Versions/A/SharedFileList.tbd and library file /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/SharedFileList.framework/Versions/A/SharedFileList are out of sync. Falling back to library file for linking.
Press [Enter] to stop listening.

touching a file named 'urk' gives the same message 3 times

python: callback called: Users/hanord/GitHub/fsevents-watcher/urk: Created IsFile
python: callback called: Users/hanord/GitHub/fsevents-watcher/urk: Created IsFile
python: callback called: Users/hanord/GitHub/fsevents-watcher/urk: Created IsFile

An AppEngine application can be composed of several modules. In this scenario, only one module gets notified of the file system event.