Issue #16719: Get rid of WindowsError. Use OSError instead

Patch by Serhiy Storchaka.
diff --git a/Lib/webbrowser.py b/Lib/webbrowser.py
index 691f7db..f1a071b 100644
--- a/Lib/webbrowser.py
+++ b/Lib/webbrowser.py
@@ -534,7 +534,7 @@
         def open(self, url, new=0, autoraise=True):
             try:
                 os.startfile(url)
-            except WindowsError:
+            except OSError:
                 # [Error 22] No application is associated with the specified
                 # file for this operation: '<URL>'
                 return False