Addresses Jim's comments on the pull request

python/MetrologyData.py

@@ -113,7 +113,7 @@ def set_ref_plane(self, plane_functor, zoffset=0, nsigma=5):
         self.resids = dz
 
         # Also define residuals with outliers removed (nsigma clipping)
-        if self.sensor.mean_filt == None:
+        if self.sensor.mean_filt is None:
             # For absolute height analysis for ITL sensors no plane will
             # have been fit at this point, so the mean and standard 
             # deviations of residuals with outliers filtered will not 

tests/test_absoluteHeightITL.py

@@ -3,8 +3,8 @@
 code in set_ref_plane that formerly crashed on this data
 """
 from __future__ import print_function
+import os
 import unittest
-#import numpy as np
 from MetrologyData import md_factory, XyzPlane
 
 class ReferencePlaneITLTestCase(unittest.TestCase):
@@ -21,7 +21,8 @@ def test_quantile_table(self):
         sensors by generating a quantile table and comparing it
         with earlier results
         """
-        infile = 'ITL_vendor_metrology_data.txt'
+        infile = os.path.join(os.environ['METROLOGYDATAANALYSISDIR'], 'tests',
+                                         'ITL_vendor_metrology_data.txt')
         dtype = 'ITL'
 
         sensorData = md_factory.create(infile, dtype=dtype)