fix travis

Author: kevinAlbs

.travis.yml

@@ -13,8 +13,8 @@ before_install:
   # https://github.com/Homebrew/homebrew-core/issues/26358
   - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew unlink python; fi
   # "brew install" can succeed but return 1 if it has "caveats".
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install mongodb || true; fi
-  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew services start mongodb; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew tap mongodb/brew && brew install mongodb-community || true; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew services start mongodb-community; fi
 
 before_script:
   # Add an IPv6 config - see the corresponding Travis issue