NameError: name 'long' is not defined using python3

[jdamp]

I want to construct a new histogram using a sliced view of another. However, when I try to construct the new histogram from the sliced one, for example with the code from the slicing documentation

>> from rootpy.plotting import Hist3D
>> a = Hist3D(10, 0, 1, 10, 0, 1, 10, 0, 1)
>> b = Hist3D(a[3:5,::2,:])

I get the following error when using python3:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jodamp/.local/lib/python3.6/site-packages/rootpy/plotting/hist.py", line 2362, in __new__
    obj = Hist3D(other.xedges, other.yedges, other.zedges, **kwargs)
  File "/home/jodamp/.local/lib/python3.6/site-packages/rootpy/decorators.py", line 225, in __get__
    result = self.method(inst)
  File "/home/jodamp/.local/lib/python3.6/site-packages/rootpy/plotting/hist.py", line 178, in xedges
    bin_to_edge_slice(self.x, self.hist.nbins(axis=0, overflow=True))]
  File "/home/jodamp/.local/lib/python3.6/site-packages/rootpy/plotting/hist.py", line 55, in bin_to_edge_slice
    s = canonify_slice(s, n)
  File "/home/jodamp/.local/lib/python3.6/site-packages/rootpy/plotting/hist.py", line 43, in canonify_slice
    if isinstance(s, (int, long)):
NameError: name 'long' is not defined

This could be fixed for example using six as done here to modify the method canonify_slice.

[ndawe]

I've fixed this in ca9cab2 but I'm waiting on some fixes to the conda ROOT builds before merging. Feel free to just implement exactly what I've changed in ca9cab2 or pull from my fork instead. Thanks for reporting!