Fix tests for If -> Piecewise

pymbolic/interop/sympy.py

@@ -125,7 +125,7 @@ class PymbolicToSympyMapper(PymbolicToSympyLikeMapper):
         elif expr.operator == ">=":
             return self.sym.GreaterThan(left, right)
         else:
-            raise NotImplementedError("Cannot understand operator {}".format(expr.operator))
+            raise NotImplementedError("Unknown operator '%s'" % expr.operator)
 
 # }}}
 

test/test_sympy.py

@@ -115,6 +115,7 @@ def test_pymbolic_to_sympy():
 
 
 def test_sympy_if_condition():
+    pytest.importorskip("sympy")
     from pymbolic.interop.sympy import PymbolicToSympyMapper, SympyToPymbolicMapper
     forward = PymbolicToSympyMapper()
     backward = SympyToPymbolicMapper()