Install R before mysql

.travis.yml

@@ -33,11 +33,11 @@ jobs:
       osx_image: xcode11.3  # Python 3.7 running on macOS 10.14.4
       language: generic       # 'language: python' is an error on Travis CI macOS
       before_install:
-        - brew install mysql
-        - brew services start mysql
         - brew install gcc@9
         - brew install https://github.com/Homebrew/homebrew-core/raw/218998d/Formula/r.rb
         - R --version
+        - brew install mysql
+        - brew services start mysql
         - brew cask install miniconda
         - eval "$(/opt/miniconda3/condabin/conda shell.bash hook)"