Python2.6 compatiblity

[bxm156]

I'm not sure if python2.6 compatibility is supposed to be supported. I don't see any specific mention in setup.py, but I encounter this error when trying to extract a variable. I believe the python syntax in the traceback is not supported in python2.6

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropemode/decorators.py", line 53, in newfunc
    return func(*args, **kwds)
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropemode/interface.py", line 52, in do_refactor
    refactoring(self, self.env).show(initial_asking=initial_asking)
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropemode/refactor.py", line 30, in show
    self.interface._check_project()
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropemode/interface.py", line 473, in _check_project
    self.open_project()
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropemode/decorators.py", line 53, in newfunc
    return func(*args, **kwds)
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropemode/interface.py", line 91, in open_project
    'create one?' % root):
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropevim.py", line 88, in y_or_n
    return self.yes_or_no(prompt)
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropevim.py", line 84, in yes_or_no
    return self.ask_values(prompt, ['yes', 'y', 'no', 'n']).lower() \
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropevim.py", line 36, in ask_values
    self._print_values(values)
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropevim.py", line 57, in _print_values
    echo('\n'.join(numbered) + '\n')
  File "/nail/home/bmarty/.dev-py/lib/python2.6/site-packages/ropevim.py", line 397, in echo
    vim.command('echo "{}"'.format(message))
ValueError: zero length field name in format