tox fail to run with latest version

Using python-tox-1.7.1-1.fc21.noarch, I see the folowing whn running tox:

 $ ./run_tests.sh
Traceback (most recent call last):
  File "/usr/bin/tox", line 9, in <module>
    load_entry_point('tox==1.7.1', 'console_scripts', 'tox')()
  File "/usr/lib/python2.7/site-packages/tox/_cmdline.py", line 25, in main
    config = parseconfig(args, 'tox')
  File "/usr/lib/python2.7/site-packages/tox/_config.py", line 47, in parseconfig
    parseini(config, inipath)
  File "/usr/lib/python2.7/site-packages/tox/_config.py", line 281, in __init__
    config)
  File "/usr/lib/python2.7/site-packages/tox/_config.py", line 346, in _makeenvconfig
    vc.commands = reader.getargvlist(section, "commands")
  File "/usr/lib/python2.7/site-packages/tox/_config.py", line 518, in getargvlist
    commandlist.append(self._processcommand(current_command))
  File "/usr/lib/python2.7/site-packages/tox/_config.py", line 550, in _processcommand
    new_word = self._replace(word)
  File "/usr/lib/python2.7/site-packages/tox/_config.py", line 666, in _replace
    return RE_ITEM_REF.sub(self._replace_match, x)
  File "/usr/lib/python2.7/site-packages/tox/_config.py", line 662, in _replace_match
    return handler(match)
  File "/usr/lib/python2.7/site-packages/tox/_config.py", line 633, in _replace_substitution
    val = self._substitute_from_other_section(sub_key)
  File "/usr/lib/python2.7/site-packages/tox/_config.py", line 627, in _substitute_from_other_section
    "substitution key %r not found" % key)
tox.ConfigError: ConfigError: substitution key 'posargs' not found