Support Python3 in Congress

Whiteboard

Gerrit topic: https://review.openstack.org/#q,topic:bug/1403209,n,z

Addressed by: https://review.openstack.org/142228
    Python 3: Fix import path for d6message in deepsix

Addressed by: https://review.openstack.org/142226
    Python 3: Fix httplib

Gerrit topic: https://review.openstack.org/#q,topic:bug/1403226,n,z

Addressed by: https://review.openstack.org/142237
    Python 3: Remove long value

Gerrit topic: https://review.openstack.org/#q,topic:bp/support-python3,n,z

Addressed by: https://review.openstack.org/199873
    Replace unicode with six.text_type

Addressed by: https://review.openstack.org/199899
    Replace dict.itervalues() with dict.values()

Addressed by: https://review.openstack.org/199908
    Remove usgae of dict.iterkeys()

Addressed by: https://review.openstack.org/199910
    Replace iterator.next() with next(iterator)

Addressed by: https://review.openstack.org/204019
    Remove usage of dict.iteritems() Replace dict.iteritems() with dict.items() Make congress python-3 compatible

Addressed by: https://review.openstack.org/204450
    Replace (int, long) with six.integer_types

Addressed by: https://review.openstack.org/204717
    Replace basestring with six.string_types

Addressed by: https://review.openstack.org/223047
    Import python 3 compatible StringIO and cStringIO

Addressed by: https://review.openstack.org/223400
    Raise python-3 compatible exceptions

Addressed by: https://review.openstack.org/223406
    python3: Switch to mox3 instead of mox

Addressed by: https://review.openstack.org/226173
    Py3: Fix import errors on amqprouter and httplib

Addressed by: https://review.openstack.org/226528
    Fix tab/space indentation

Addressed by: https://review.openstack.org/226532
    Fix syntax of except for Python 3

Addressed by: https://review.openstack.org/226536
    Update hacking to version 0.10

Addressed by: https://review.openstack.org/226537
    Replace xrange() with six.moves.range

Addressed by: https://review.openstack.org/226538
    Fix usage of dict methods on Python 3

Addressed by: https://review.openstack.org/226540
    Replace httplib import with six.moves.http_client

Addressed by: https://review.openstack.org/226542
    Fix relative imports for Python 3

Addressed by: https://review.openstack.org/226544
    Add nested context manager to tests.base for py3

Addressed by: https://review.openstack.org/226815
    Replace local copy of dateutil 1.5, use dependency

Addressed by: https://review.openstack.org/242305
    Python3-readiness for antlr3 pieces

Addressed by: https://review.openstack.org/248946
    Python3 readiness for congress/datalog

Addressed by: https://review.openstack.org/252165
    Python3 readiness for congress/datasources

Addressed by: https://review.openstack.org/253279
    Python3 readiness for congress/api

Addressed by: https://review.openstack.org/253298
    Python3 readiness for congress (misc changes)

Addressed by: https://review.openstack.org/263464
    Use python3 print, division, import

Addressed by: https://review.openstack.org/263466
    Replace raise <str> by raise <Exception>

Addressed by: https://review.openstack.org/263477
    Replace antlr3 symlinking by sys.path

Work Items