Description of problem:

When trying to build in EL6, I get the following:
+ /usr/bin/python setup.py build
Traceback (most recent call last):
  File "setup.py", line 2, in <module>
    from turbogears.finddata import find_package_data
  File "/usr/lib/python2.6/site-packages/turbogears/__init__.py", line 10, in <module>
    from turbogears.controllers import (absolute_url, expose, flash, validate,
  File "/usr/lib/python2.6/site-packages/turbogears/controllers.py", line 19, in <module>
    from turbogears import view, database, errorhandling, config
  File "/usr/lib/python2.6/site-packages/turbogears/view/__init__.py", line 1, in <module>
    from turbogears.view import base
  File "/usr/lib/python2.6/site-packages/turbogears/view/base.py", line 31, in <module>
    from turbogears.i18n import get_locale, gettext
  File "/usr/lib/python2.6/site-packages/turbogears/i18n/__init__.py", line 4, in <module>
    from turbogears.i18n.tg_gettext import (gettext, ngettext, install,
  File "/usr/lib/python2.6/site-packages/turbogears/i18n/tg_gettext.py", line 8, in <module>
    from turbojson.jsonify import jsonify
ImportError: No module named turbojson.jsonify

This is because python-tgcaptcha BuildRequires TurboGears, and TurboGears Requires python-turbojson13

But python-turbojson13 is designed to be parallel installable with the python-turbojson package from RHEL 6.

Toshio (who maintains python-turbojson13) explained ot me on IRC that python-turbojson13 is designed to be parallel installable with the python-turbojson package from RHEL 6, and as such it can't be imported straight away.

So applications are responsible for jumping through a few hoops in order to import it:
>>> __requires__ = ['TurboJson >= 1.3']
>>> import pkg_resources

Then the import works fine.

Attaching a patch to fix the build.