Homebrew updated to 3.8 yesterday.

Author: henryiii

.travis.yml

@@ -147,9 +147,9 @@ matrix:
     osx_image: xcode7.3
     env: PYTHON=2.7 CPP=14 CLANG CMAKE=1
   - os: osx
-    name: Python 3.7, c++14, AppleClang 9, Debug build
+    name: Python 3.8, c++14, AppleClang 9, Debug build
     osx_image: xcode9.4
-    env: PYTHON=3.7 CPP=14 CLANG DEBUG=1
+    env: PYTHON=3.8 CPP=14 CLANG DEBUG=1
   # Test a PyPy 2.7 build
   - os: linux
     dist: trusty