old_contents: from discretize.BaseMesh import BaseMesh
  from discretize.TensorMesh import TensorMesh
  from discretize.CylMesh import CylMesh
  from discretize.CurvilinearMesh import CurvilinearMesh
  from discretize.TreeMesh import TreeMesh
  from discretize import Tests
  
  __version__   = '0.1.5'
  __author__    = 'SimPEG Team'
  __license__   = 'MIT'
  __copyright__ = '2013 - 2017, SimPEG Developers, http://simpeg.xyz'
  
new_contents: from discretize.BaseMesh import BaseMesh
  from discretize.TensorMesh import TensorMesh
  from discretize.CylMesh import CylMesh
  from discretize.CurvilinearMesh import CurvilinearMesh
  from discretize import Tests
  
  try:
      from discretize.TreeMesh import TreeMesh
  except ImportError:
      print(
          """
          TreeMesh not imported. You need to run:
  
          python setup.py install
  
          to build the TreeMesh cython code.
          """
      )
  
  __version__   = '0.1.5'
  __author__    = 'SimPEG Team'
  __license__   = 'MIT'
  __copyright__ = '2013 - 2017, SimPEG Developers, http://simpeg.xyz'
  
subject: add a try except for importing the TreeMesh. This should resolve #26