Fix macOS tests (#6437)

* Don't try to install installed packages.

* Test with any version of python3 on macOS.

* move file and fix mode

* ignore stderr too

* remove extra set -e

* no linux failures

.travis.yml

@@ -12,7 +12,7 @@ before_install:
   - cp .travis.yml /tmp/travis.yml
   - git pull origin master --strategy=recursive --strategy-option=theirs --no-edit
   - if ! git diff .travis.yml /tmp/travis.yml ; then echo "Please merge master into test-everything"; exit 1; fi
-  - '([ $TRAVIS_OS_NAME == linux ] && dpkg -s libaugeas0) || (brew update && brew install augeas && brew upgrade python python3 && brew link python)'
+  - '[ "$TRAVIS_OS_NAME" != osx ] || tests/travis-macos-setup.sh'
 
 before_script:
   - 'if [ $TRAVIS_OS_NAME = osx ] ; then ulimit -n 1024 ; fi'
@@ -121,7 +121,7 @@ matrix:
       env: TOXENV=py27
       os: osx
     - language: generic
-      env: TOXENV=py37
+      env: TOXENV=py3
       os: osx
 
 

tests/travis-macos-setup.sh

@@ -0,0 +1,17 @@
+#!/bin/bash -e
+#
+# Set up the test environment for macOS on Travis.
+
+# Install the given package with brew if it's not already installed.
+brew_install() {
+    if ! brew list "$1" > /dev/null 2>&1; then
+        brew install "$1"
+    fi
+}
+
+brew_install augeas
+brew_install python
+brew_install python3
+
+# Ensure we use python from brew.
+brew link python