Chain commands by &&

See https://github.com/rust-lang-nursery/rustfmt/pull/2229/files#r155177741 for reasoning

Author: CAD97

.travis.yml

@@ -21,12 +21,12 @@ addons:
 before_script:
 - |
   if [ $TRAVIS_OS_NAME = 'osx' ]; then
-    brew install python3
-    virtualenv env -p python3
-    source env/bin/activate
-    pip install 'travis-cargo<0.2'
+    brew install python3 &&
+    virtualenv env -p python3 &&
+    source env/bin/activate &&
+    pip install 'travis-cargo<0.2' &&
   else
-    pip install 'travis-cargo<0.2' --user
+    pip install 'travis-cargo<0.2' --user &&
     export PATH="$(python -m site --user-base)/bin:$PATH"
   fi