Task #3249: Added logic to really test success/failure of test_sm script

CEP/PyBDSM/test/test_sm.py

 import lofar.bdsm as bdsm
+import sys
 
+# Process the image
 img = bdsm.process_image('test_sm.in')
+
+# List of operations that must have been done on `img`.
+operations = [
+    'readimage', 'collapse', 'preprocess', 'rmsimage', 'threshold', 
+    'islands', 'gausfit', 'gaul2srl', 'make_residimage', 'wavelet_atrous', 
+    'shapelets', 'spectralindex', 'polarisation', 'psf_vary', 'cleanup'
+]
+
+# Return exit status 0 if everything went fine, otherwise return 1.
+if img and all(oper in img.completed_Ops for oper in operations):
+    sys.exit(0)
+else:
+    sys.exit(1)
+