Use contextlib to workaround Python 2.6 zipfile not supporting 'with' statement.
Use contextlib to workaround Python 2.6 zipfile not supporting 'with' statement.

umbrant/dist_test,cloudera/dist_test,cloudera/dist_test,xiao-chen/dist_test,umbrant/dist_test,umbrant/dist_test,cloudera/dist_test,cloudera/dist_test,umbrant/dist_test,xiao-chen/dist_test,xiao-chen/dist_test,xiao-chen/dist_test