Why can't I compute the ehrhart polynomial of a polytope?

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I'm getting an error message when I try to compute the ehrhart polynomial of a polytope:

┌────────────────────────────────────────────────────────────────────┐
│ SageMath version 7.3, Release Date: 2016-08-04                     │
│ Type "notebook()" for the browser-based notebook interface.        │
│ Type "help()" for help.                                            │
└────────────────────────────────────────────────────────────────────┘
sage: P = polytopes.simplex(3)
sage: P.ehrhart_polynomial()
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
<ipython-input-2-9033e1d690fd> in <module>()
----> 1 P.ehrhart_polynomial()

/home/brian/.computer_algebra_systems/sage-7.0/local/lib/python2.7/site-packages/sage/geometry/polyhedron/base_ZZ.pyc in ehrhart_polynomial(self, verbose, dual, irrational_primal, irrational_all_primal, maxdet, no_decomposition, compute_vertex_cones, smith_form, dualization, triangulation, triangulation_max_height, **kwds)
    317             else:
    318                 err = ":\n" + err
--> 319             raise RuntimeError("LattE integrale failed with exit code {} to execute {}".format(ret_code, ' '.join(args)) + err.strip())
    320 
    321         p = ans.splitlines()[-2]

RuntimeError: LattE integrale failed with exit code 127 to execute count --ehrhart-polynomial --redundancy-check=none --cdd /dev/stdin:
count: error while loading shared libraries: libntl.so.19: cannot open shared object file: No such file or directory
sage: