add websocket to requirements.txt

We just just install all the packages we need

plexapi/alert.py

@@ -1,8 +1,10 @@
 # -*- coding: utf-8 -*-
 import json
 import threading
+
+import websocket
+
 from plexapi import log
-from plexapi.exceptions import Unsupported
 
 
 class AlertListener(threading.Thread):
@@ -12,9 +14,6 @@ class AlertListener(threading.Thread):
         alerts you must call .start() on the object once it's created. When calling
         `PlexServer.startAlertListener()`, the thread will be started for you.
 
-        In order to use this feature, you must have websocket-client installed in your Python path.
-        This can be installed vis pip `pip install websocket-client`.
-
         Parameters:
             server (:class:`~plexapi.server.PlexServer`): PlexServer this listener is connected to.
             callback (func): Callback function to call on recieved messages. The callback function
@@ -30,17 +29,12 @@ class AlertListener(threading.Thread):
         super(AlertListener, self).__init__()
 
     def run(self):
-        # try importing websocket-client package
-        try:
-            import websocket
-        except:
-            raise Unsupported('Websocket-client package is required to use this feature.')
         # create the websocket connection
         url = self._server.url(self.key).replace('http', 'ws')
         log.info('Starting AlertListener: %s', url)
         self._ws = websocket.WebSocketApp(url,
-            on_message=self._onMessage,
-            on_error=self._onError)
+                                          on_message=self._onMessage,
+                                          on_error=self._onError)
         self._ws.run_forever()
 
     def stop(self):

requirements.txt

@@ -3,3 +3,4 @@
 # pip install -r requirments.txt
 #---------------------------------------------------------
 requests
+websocket