Switch command line parser to argparse

[FiloSottile]

From http://docs.python.org/2/library/optparse.html

Deprecated since version 2.7:
The optparse module is deprecated and will not be developed further;
development will continue with the argparse module.

Follow http://docs.python.org/2/library/argparse.html#upgrading-optparse-code

[ocisly]

@FiloSottile @phihag If I implement this (obviously quite a bit of work, but worth it in my mind), will it be merged? What about Python 2.6, where argparse is available on PyPI but not as part of the standard library?

By the way, how long do we plan to support 2.6 since it has reached end of life and is receiving fixes, security or otherwise, as of October 2013:

With the 2.6.9 release, and five years after its first release, the Python 2.6 series is now officially retired. All official maintenance for Python 2.6, including security patches, has ended. For ongoing maintenance releases, please see the Python 2.7 series.

[phihag]

We will support Python 2.6 for quite some time (basically, until RHEL drops support). Since I do not see a pressing need to switch to argparse anyways (there are no security implications, and virtually no differences for our users). I'm therefore closing this issue, to be reopened after we have dropped 2.6 support, or a new 3.x version drops optparse.

[zedxxx]

No argparse! Docopt is the best: https://github.com/docopt/docopt