Use oslo-config-2013.1b4

The cfg API is now available via the oslo-config library, so switch to
it and remove the copied-and-pasted version.

Add the 2013.1b4 tarball to tools/pip-requires - this will be changed
to 'oslo-config>=2013.1' when oslo-config is published to pypi. This
will happen in time for grizzly final.

Add dependency_links to setup.py so that oslo-config can be installed
from the tarball URL specified in pip-requires.

Remove the 'deps = pep8==1.3.3' from tox.ini as it means all the other
deps get installed with easy_install which can't install oslo-config
from the URL.

Make tools/hacking.py include oslo in IMPORT_EXCEPTIONS like it already
does for paste. It turns out imp.find_module() doesn't correct handle
namespace packages.

Retain dummy cfg.py file until keystoneclient middleware has been
updated (I18c450174277c8e2d15ed93879da6cd92074c27a).

Change-Id: I4815aeb8a9341a31a250e920157f15ee15cfc5bc

setup.py

@@ -20,6 +20,7 @@ import setuptools
 from nova.openstack.common import setup as common_setup
 
 requires = common_setup.parse_requirements()
+depend_links = common_setup.parse_dependency_links()
 project = 'nova'
 
 setuptools.setup(
@@ -42,6 +43,7 @@ setuptools.setup(
       cmdclass=common_setup.get_cmdclass(),
       packages=setuptools.find_packages(exclude=['bin', 'smoketests']),
       install_requires=requires,
+      dependency_links=depend_links,
       include_package_data=True,
       test_suite='nose.collector',
       setup_requires=['setuptools_git>=0.4'],