Can't get jupter to start

```
Traceback (most recent call last):
File "/usr/bin/jupyter-notebook", line 3, in
from notebook.notebookapp import main
File "/usr/lib/python3.6/site-packages/notebook/notebookapp.py", line 61, in
from .services.kernels.kernelmanager import MappingKernelManager
File "/usr/lib/python3.6/site-packages/notebook/services/kernels/kernelmanager.py", line 16, in
from jupyter_client.multikernelmanager import MultiKernelManager
File "/usr/lib/python3.6/site-packages/jupyter_client/__init__.py", line 7, in
from .manager import KernelManager, run_kernel
File "/usr/lib/python3.6/site-packages/jupyter_client/manager.py", line 32, in
from .session import Session
File "/usr/lib/python3.6/site-packages/jupyter_client/session.py", line 61, in
from jupyter_client.jsonutil import extract_dates, squash_dates, date_default
File "/usr/lib/python3.6/site-packages/jupyter_client/jsonutil.py", line 11, in
from dateutil.parser import parse as _dateutil_parse
File "/usr/lib/python3.6/site-packages/dateutil/parser.py", line 158
l.append("%s=%s" % (attr, `value`))
^
SyntaxError: invalid syntax

I tried uninstalling and reinstalling

Start with the traceback from /usr/bin/jupyter-notebook and inspect the imports through notebook/services/kernels/kernelmanager.py, jupyter_client/manager.py, and dateutil/parser.py. Reproduce the startup failure while checking the Python and python-dateutil versions; done means Jupyter Notebook starts without the SyntaxError.

Written by the indexing model from the issue text.