Fix Uisotropy bug in the GeneratorSite class.

GeneratorSite did not set the Uisotropy attribute (bug introduced
in be75a8f).  Also fixes the simplepdftwophase.py example in srfit.

Author: pavoljuhas

diffpy/Structure/SymmetryUtilities.py

@@ -444,6 +444,7 @@ def _findUSpace(self):
         mxcols = numpy.argmax(numpy.fabs(Usp6), axis=1)
         Usp6 /= Usp6[mxrows,mxcols].reshape(-1, 1)
         self.Uspace = numpy.tensordot(Usp6, self.Ucomponents, axes=(1, 0))
+        self.Uisotropy = (len(self.Uspace) == 1)
         return
 
     def _findUParameters(self):

diffpy/Structure/tests/TestSymmetryUtilities.py

@@ -391,6 +391,17 @@ def test_corepos(self):
         self.assertTrue(sc.coremap[4] == range(4, 4+192))
         return
 
+    def test_Uisotropy(self):
+        """check isotropy value for ADP-s at specified sites.
+        """
+        sg225 = GetSpaceGroup(225)
+        corepos = [[0, 0, 0], [0.1, 0.13, 0.17]]
+        eau = ExpandAsymmetricUnit(sg225, corepos)
+        self.assertEqual([True, False], eau.Uisotropy)
+        sc = SymmetryConstraints(sg225, eau.expandedpos)
+        self.assertEqual(4 * [True] + 192 * [False], sc.Uisotropy)
+        return
+
 #   def test__findConstraints(self):
 #       """check SymmetryConstraints._findConstraints()
 #       """