From a2497e0854a1672e513ed518752797f9231b6a12 Mon Sep 17 00:00:00 2001
From: Job Evers-Meltzer <jobevers@users.noreply.github.com>
Date: Mon, 19 Dec 2016 15:28:20 -0800
Subject: [PATCH] Fix error on brew when package is already installed

---
 packaging/travis/setup_osx.sh | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/packaging/travis/setup_osx.sh b/packaging/travis/setup_osx.sh
index 503882675..f4a5eb659 100755
--- a/packaging/travis/setup_osx.sh
+++ b/packaging/travis/setup_osx.sh
@@ -7,5 +7,19 @@ wget https://www.python.org/ftp/python/2.7.11/python-2.7.11-macosx10.6.pkg
 sudo installer -pkg python-2.7.11-macosx10.6.pkg -target /
 pip install -U pip
 brew update
-brew install openssl
-brew link --force openssl
+
+# follow this pattern to avoid failing if its already
+# installed by brew:
+# http://stackoverflow.com/a/20802425
+if brew ls --versions gmp > /dev/null; then
+    echo 'gmp is already installed by brew'
+else
+    brew install gmp
+fi
+
+if brew ls --versions openssl > /dev/null; then
+    echo 'openssl is already installed by brew'
+else
+    brew install openssl
+    brew link --force openssl
+fi