Timeout for caching in TravisCI

.travis.yml

@@ -12,7 +12,6 @@ env:
   - JOB=DOCS
   - JOB=BUILD_AND_TEST
   - JOB=PRE_COMMIT
-
 addons:
   apt:
     packages:
@@ -49,8 +48,12 @@ before_install:
   # Paddle is using protobuf 3.1 currently. Protobuf 3.2 breaks the compatibility. So we specify the python 
   # protobuf version.
   - pip install numpy wheel 'protobuf==3.1' sphinx recommonmark sphinx-rtd-theme==0.1.9 virtualenv pre-commit requests==2.9.2 LinkChecker
+  - |
+    function timeout() { perl -e 'alarm shift; exec @ARGV' "$@"; }
 script:
-  - paddle/scripts/travis/main.sh
+  - | 
+    timeout 2580 paddle/scripts/travis/main.sh  # 43min timeout
+    RESULT=$?; if [ $RESULT -eq 0 ] || [ $RESULT -eq 142 ]; then true; else false; fi;
 notifications:
   email:
     on_success: change