Ceph

As more distributions start supporting python 3 (and in some cases Python 3 only) it is becoming quite problematic to
just rely on lines like:

#!/usr/bin/env python

When distros start supporting python 3, scripts are expected to specify python 2 with:

#!/usr/bin/env python2

However, this is an incompatible way to specify the python version as systems that ship with python 2
will break on that line.

Some opinions from the community are:

• Port everything to Go (or something with no dependencies)
• Package/embed a Python interpreter of our choosing (e.g. Python 2.7) to work for our scripts

My suggestion is to do a single code-base that supports 2.6, 2.7, and 3.4.

It is not that difficult to do so, and there would need to be 2 requirements for this to happen:

• a test harness where we can add more/different interpreters to test against (making sure the same
  code works for all the versions we want to support). This is already somewhat in place for
  ceph-brag (see src/test/python/) and more to come with #8458

• a library that has reusable common modules that work correctly independently of the python version. This is kind
  of what the `six` library does, and we would either need to include `six` with Ceph and allow us to import from it
  or have one of our own with our very specific needs.