Merge pull request #321 from robbuckley/homebrew-xcode8

MRG: remove brew update to avoid problems with older macos images

Update causing errors; update was there for bug that is now old.

tests/test_multibuild.sh

@@ -11,10 +11,6 @@ if [ -n "$IS_OSX" ]; then
     source osx_utils.sh
     MB_PYTHON_OSX_VER=${MB_PYTHON_OSX_VER:-$(macpython_sdk_for_version $MB_PYTHON_VERSION)}
 
-    # To work round:
-    # https://travis-ci.community/t/syntax-error-unexpected-keyword-rescue-expecting-keyword-end-in-homebrew/5623
-    brew update
-
     get_macpython_environment $MB_PYTHON_VERSION ${VENV:-""} $MB_PYTHON_OSX_VER
     source tests/test_python_install.sh
     source tests/test_fill_pyver.sh