Correcting bug in window validation

Author: carlosdanielcsantos

pandas/core/window.py

@@ -1057,7 +1057,8 @@ def validate(self):
             raise ValueError("window must be an integer")
         elif self.window < 0:
             raise ValueError("window must be non-negative")
-        elif self.closed is not None:
+
+        if not self.is_datetimelike and self.closed is not None:
             raise ValueError("closed only implemented for datetimelike "
                                          "and offset based windows")