a.rb

epinux@Debian-70-wheezy-64-minimal:~$ ipython3
Traceback (most recent call last):
  File "/home/epilib/Envs/env1/lib/python3.4/site-packages/IPython/utils/traitlets.py", line 407, in __get__
    value = obj._trait_values[self.name]
AttributeError: 'List' object has no attribute 'name'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/home/epilib/Envs/env1/bin/ipython3", line 5, in <module>
    start_ipython()
  File "/home/epilib/Envs/env1/lib/python3.4/site-packages/IPython/__init__.py", line 118, in start_ipython
    return launch_new_instance(argv=argv, **kwargs)
  File "/home/epinux/dev/ipython/src/traitlets/traitlets/config/application.py", line 590, in launch_instance
    app = cls.instance(**kwargs)
  File "/home/epinux/dev/ipython/src/traitlets/traitlets/config/configurable.py", line 380, in instance
    inst = cls(*args, **kwargs)
  File "<string>", line 2, in __init__
  File "/home/epinux/dev/ipython/src/traitlets/traitlets/config/application.py", line 75, in catch_config_error
    return method(app, *args, **kwargs)
  File "/home/epilib/Envs/env1/lib/python3.4/site-packages/IPython/core/application.py", line 185, in __init__
    super(BaseIPythonApplication, self).__init__(**kwargs)
  File "/home/epinux/dev/ipython/src/traitlets/traitlets/config/application.py", line 245, in __init__
    if self.__class__ not in self.classes:
  File "/home/epilib/Envs/env1/lib/python3.4/site-packages/IPython/utils/traitlets.py", line 424, in __get__
    raise TraitError('Unexpected error in TraitType: '
IPython.utils.traitlets.TraitError: Unexpected error in TraitType: default value not set properly
epinux@Debian-70-wheezy-64-minimal:~$