I've tried to install it in a MAC using PIP and PIP3 and I get the same error:

Command "/usr/local/opt/python/bin/python3.7 -u -c "import setuptools, tokenize;file='/private/var/folders/0s/rkvsfhzn2930_3902mpks9lm0000gn/T/pip-install-3cscl6kq/watchdog/setup.py';f=getattr(tokenize, 'open', open)(file);code=f.read().replace('\r\n', '\n');f.close();exec(compile(code, file, 'exec'))" install --record /private/var/folders/0s/rkvsfhzn2930_3902mpks9lm0000gn/T/pip-record-qr49cvd0/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /private/var/folders/0s/rkvsfhzn2930_3902mpks9lm0000gn/T/pip-install-3cscl6kq/watchdog/

I'm using:
macOS Mojave 10.14.5