XPRESS Solver Error : AttributeError: 'NoneType' object has no attribute 'problem'

[kdheepak]

I've pasted the traceback below :

Traceback (most recent call last):
  File "model.py", line 15, in <module>
    solver.solve(model)
  File "/Users/$USER/anaconda/lib/python2.7/site-packages/pyomo/opt/base/solvers.py", line 587, in solve
    result = self._postsolve()
  File "/Users/$USER/anaconda/lib/python2.7/site-packages/pyomo/opt/solver/shellcmd.py", line 267, in _postsolve
    results = self.process_output(self._rc)
  File "/Users/$USER/anaconda/lib/python2.7/site-packages/pyomo/opt/solver/shellcmd.py", line 329, in process_output
    self.process_soln_file(results)
  File "/Users/$USER/anaconda/lib/python2.7/site-packages/pyomo/solvers/plugins/solvers/XPRESS.py", line 336, in process_soln_file
    results.problem.number_of_objectives=1
AttributeError: 'NoneType' object has no attribute 'problem'