Check if paddle is installed when unittest. (#134)

paddle/.set_python_path.sh

@@ -22,15 +22,21 @@
 # It same as PYTHONPATH=${YOUR_PYTHON_PATH}:$PYTHONPATH {exec...}
 #
 
-PYPATH=""
-set -x
-while getopts "d:" opt; do
+if ! python -c "import paddle" >/dev/null 2>/dev/null; then
+  PYPATH=""
+  set -x
+  while getopts "d:" opt; do
     case $opt in
       d)
         PYPATH=$OPTARG
         ;;
     esac
-done
-shift $(($OPTIND - 1))
-export PYTHONPATH=$PYPATH
-$@
+  done
+  shift $(($OPTIND - 1))
+  export PYTHONPATH=$PYPATH
+  $@
+else
+  echo "paddle package is already in your PYTHONPATH. But unittest need a clean environment."
+  echo "Please uninstall paddle package before start unittest. Try to 'pip uninstall paddle'"
+  exit 1
+fi