all Python cells throw AttributError: 'list' object has no attribute 'isspace'

OSX 10.11.3
Atom 1.5.3
Python 3.5.1
apm: jupyter-notebook: 0.0.9
pip: notebook: 4.1.0

Every time I try to execute a cell, this is the result:

```
Traceback (most recent call last):

File "/usr/local/lib/python3.5/site-packages/ipykernel/ipkernel.py", line 175, in do_execute
shell.run_cell(code, store_history=store_history, silent=silent)

File "/usr/local/lib/python3.5/site-packages/IPython/core/interactiveshell.py", line 2629, in run_cell
if (not raw_cell) or raw_cell.isspace():

AttributeError: 'list' object has no attribute 'isspace'
```

Start with the traceback in ipykernel/ipkernel.py and IPython/core/interactiveshell.py, focusing on the value passed as raw_cell during execution. Reproduce the failure with the listed Atom, jupyter-notebook, and Python versions, then verify that executing a Python cell no longer raises the reported AttributeError.

Written by the indexing model from the issue text.