React-native: watchman - no-pretty get-sockname retornado com código de saída nulo

Eu sigo o guia para iniciantes na página nativa do react. Ao executar o comando react-native run-ios , obtive o seguinte erro:

watchman--no-pretty get-sockname returned with exit code null dyld: Library not loaded: /usr/local/opt/pcre/lib/libpcre.1.dylib
  Referenced from: /usr/local/Cellar/watchman/4.5.0/libexec/bin/watchman
  Reason: image not found

 ERROR  watchman--no-pretty get-sockname returned with exit code null dyld: Library not loaded: /usr/local/opt/pcre/lib/libpcre.1.dylib
  Referenced from: /usr/local/Cellar/watchman/4.5.0/libexec/bin/watchman
  Reason: image not found

Error: watchman--no-pretty get-sockname returned with exit code null dyld: Library not loaded: /usr/local/opt/pcre/lib/libpcre.1.dylib
  Referenced from: /usr/local/Cellar/watchman/4.5.0/libexec/bin/watchman
  Reason: image not found

meu sistema: macos 10.11.6, nó 6.2.2