Backported check_call for setup.py
Use the old "except" syntax

except <expression> as <name>: was added in Python 2.6
Separate try..except and try..finally

try..except..finally was added in Python 2.5
Make the relative imports explicit and absolute

Relative imports were added in Python 2.5.

rhelup/__init__.py can use relative imports to import other rhelup modules, but
it only imports logutils so there's not much point in making that inconsistent.
Don't use __package__.

Instead use a pkgname variable set from __name__ in rhelup/__init__.py.
__init__.py imports logutils, so derive pkgname in logutils by splitting the
__name__ there (rhelup.logutils) on '.'

__package__ was added in Python 2.6.
Do not use with statements.

with was added in Python 2.5.

Dang, faking __exit__ looks gross.
Expand conditional expressions into if..else statements

Conditional expressions were added in Python 2.5
Provide an implementation of CalledProcessError

CalledProcessError was added in Python 2.5
Use the old syntax for octal literals.

The 0o... syntax was added in Python 2.6
Use openssl via m2crypto for digests instead of hashlib

hashlib was added in Python 2.5
Don't use collections.namedtuple

namedtuple was added in Python 2.6