Skip tests when periodictable is not installed.

Display gentle warning rather than failed tests.

Author: pavoljuhas

diffpy/srreal/tests/testatomradiitable.py

@@ -7,6 +7,7 @@
 import os
 import unittest
 import cPickle
+from diffpy.srreal.tests.testutils import TestCasePeriodictableOptional
 from diffpy.srreal.atomradiitable import AtomRadiiTable, CovalentRadiiTable
 from diffpy.srreal.atomradiitable import ConstantRadiiTable
 
@@ -109,7 +110,7 @@ def test_toString(self):
 # End of class TestAtomRadiiTable
 
 ##############################################################################
-class TestCovalentRadiiTable(unittest.TestCase):
+class TestCovalentRadiiTable(TestCasePeriodictableOptional):
 
     def setUp(self):
         self.rtb = CovalentRadiiTable()

diffpy/srreal/tests/testutils.py

@@ -25,6 +25,18 @@
     TestCaseObjCrystOptional = object
     logging.warning('Compiled without ObjCryst, pyobjcryst tests skipped.')
 
+# class TestCasePeriodictableOptional
+
+try:
+    import periodictable
+    from unittest import TestCase as TestCasePeriodictableOptional
+except ImportError:
+    TestCasePeriodictableOptional = object
+    logging.warning('Cannot import periodictable, periodictable tests skipped.')
+except TypeError:
+    TestCaseObjCrystOptional = object
+    logging.warning('Compiled without ObjCryst, pyobjcryst tests skipped.')
+
 # helper functions
 
 def datafile(filename):