S3 Tests run on the impala-ec2 label are failing on toolchain init b/c impala-python command cannot be found

We've seen this failure intermitently in the past and have been unable to track down the cause. I've seen it a few times recently.

http://sandbox.jenkins.cloudera.com/job/record-service-s3/387/console
17:59:51 /data/jenkins/workspace/record-service-s3/repos/Impala
17:59:51 +++ '[' -n true ']'
17:59:51 +++ echo '>>> Bootstrapping toolchain.'
17:59:51 >>> Bootstrapping toolchain.
17:59:51 +++ cd /data/jenkins/workspace/record-service-s3/repos/RecordServiceClient
17:59:51 +++ impala-python jenkins/bootstrap_toolchain.py
17:59:51 /data/jenkins/workspace/record-service-s3/repos/RecordServiceClient/jenkins/build_impala.sh: line 28: impala-python: command not found
17:59:51 +++ echo 'toolchain bootstrap failed'
17:59:51 toolchain bootstrap failed