old_contents: """
  Testing utilities
  """
  import os
  import unittest
  import numpy as np
  import rastercube.jgrid as jgrid
  from numpy.testing import assert_array_equal
  
  
  def get_rastercube_dir():
      import rastercube
      return os.path.dirname(rastercube.__file__)
  
  
  def get_testdata_dir():
      assert 'RASTERCUBE_TEST_DATA' in os.environ, 'You must define TERRAI_TEST_DATA'
      datadir = os.environ['RASTERCUBE_TEST_DATA']
      assert os.path.exists(datadir), 'testdata dir %s does not exist' % datadir
      return datadir
  
  
  class RasterCubeTest(unittest.TestCase):
      def setUp(self):
          # Point the datadir to the test datadir
          os.environ['RASTERCUBE_DATA'] = get_testdata_dir()
  
new_contents: """
  Testing utilities
  """
  import os
  import unittest
  import numpy as np
  import rastercube.jgrid as jgrid
  from numpy.testing import assert_array_equal
  
  
  def get_rastercube_dir():
      import rastercube
      return os.path.dirname(rastercube.__file__)
  
  
  def get_testdata_dir():
      assert 'RASTERCUBE_TEST_DATA' in os.environ, 'You must define RASTERCUBE_TEST_DATA'
      datadir = os.environ['RASTERCUBE_TEST_DATA']
      assert os.path.exists(datadir), 'testdata dir %s does not exist' % datadir
      return datadir
  
  
  class RasterCubeTest(unittest.TestCase):
      def setUp(self):
          # Point the datadir to the test datadir
          os.environ['RASTERCUBE_DATA'] = get_testdata_dir()
  
subject: Fix assert message