sys.maxsize is the maximum length of a container.

[bfroehle]

From the Python documentation:

sys.maxsize:
The largest positive integer supported by the platform's
Py_ssize_t type, and thus the maximum size lists, strings,
dicts, and many other containers can have.

From our usage in the traitlet, it's clear that what we really
mean is sys.maxsize (not sys.maxint). In general
sys.maxsize >= sys.maxint so this patch shouldn't have any
actual impact.

I noticed this only because Python 3 has no sys.maxint attribute.
This is our only usage of sys.maxint which isn't protected by a
if not PY3 statement.

[takluyver]

Thanks, that looks sensible. Merging now.