PROTON-2174: Updated travis yml with brew update workaround for bundle issue.
diff --git a/.travis.yml b/.travis.yml
index 28ad8a0..881ad34 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -74,6 +74,9 @@
       - jsoncpp
       - libuv
       - swig
+# update:true workaround as of Feb. 22/20 as per
+# https://travis-ci.community/t/macos-build-fails-because-of-homebrew-bundle-unknown-command/7296/10
+    update: true 
 
 install:
 - python -m pip install --user --upgrade pip