Test for pandas-dev#16726. unittest that ensures datetime is understood

Author: hussain

pandas/tests/series/test_datetime_values.py

@@ -409,3 +409,11 @@ def test_date_tz(self):
                            date(2015, 11, 22)])
         assert_series_equal(s.dt.date, expected)
         assert_series_equal(s.apply(lambda x: x.date()), expected)
+
+    def test_datetime_understood(self):
+        # Ensures it doesn't throw an exception reported in #16726
+        try:
+            pd.Series(pd.date_range("2012-01-01", periods=3)) - pd.offsets.DateOffset(days=6)
+        except Exception:
+            assert 'data type "datetime" not understood'
+