Revert "Allow overriding or adding custom event handlers to event dis…

…patch map (#814)"

This reverts commit be845f3.

Fixes #830.

src/watchdog/events.py

@@ -260,16 +260,6 @@ class FileSystemEventHandler:
     Base file system event handler that you can override methods from.
     """
 
-    def __init__(self):
-        # Allow overriding or adding custom event handlers to event dispatch map.
-        self.event_dispatch_map = {
-            EVENT_TYPE_CREATED: self.on_created,
-            EVENT_TYPE_DELETED: self.on_deleted,
-            EVENT_TYPE_MODIFIED: self.on_modified,
-            EVENT_TYPE_MOVED: self.on_moved,
-            EVENT_TYPE_CLOSED: self.on_closed,
-        }
-
     def dispatch(self, event):
         """Dispatches events to the appropriate methods.
 
@@ -279,7 +269,13 @@ def dispatch(self, event):
             :class:`FileSystemEvent`
         """
         self.on_any_event(event)
-        self.event_dispatch_map[event.event_type](event)
+        {
+            EVENT_TYPE_CREATED: self.on_created,
+            EVENT_TYPE_DELETED: self.on_deleted,
+            EVENT_TYPE_MODIFIED: self.on_modified,
+            EVENT_TYPE_MOVED: self.on_moved,
+            EVENT_TYPE_CLOSED: self.on_closed,
+        }[event.event_type](event)
 
     def on_any_event(self, event):
         """Catch-all event handler.