Draft: Use Skein to launch Yarn app in dev instances

This commit is a first step to enable Skein in dev instances. AIRFLOW_INSTANCE_NAME is one of the env variable used to build the dags default args.

Now, the proper Kerberos access must be forwarded.

I have already tried:

• to create my own keytab

  ktutil
  addent -password -p myname -k 1 -e RC4-HMAC
  wkt ~/airflow/airflow.keytab

But this is the wrong encryption.

• to use analytics.keytab But I may have to run the whole process with kerberos-run-command.sh.

Note: Skein is collecting those errors very roughly here: https://github.com/jcrist/skein/blob/master/skein/core.py#L256 It is not ideal for debugging.