Apprise notifications (#43)

* issue #4 Adding settings screen for apprise URLS
* Adding test notification mechanism

* Move Worker module to own class file

* Adding basic notification URL runner

* Tests for notifications

* Tweak readme with notification info

* Move notification test to main test_backend.py

* Fix spacing

* Adding notifications screenshot

* Cleanup more files from test

* Offer send notification test on individual edits and main/default

* Process global notifications

* All branches test

* Wrap worker notification process in try/catch, use global if nothing set

* Fix syntax

* Handle exception, increase wait time for liveserver to come up

* Fixing test setup

* remove debug

* Split tests into their own totally isolated setups, if you know a better way to make live_server() work, MR :)

* Tidying up lint/imports

backend/update_worker.py

@@ -0,0 +1,67 @@
+import threading
+import queue
+
+# Requests for checking on the site use a pool of thread Workers managed by a Queue.
+class update_worker(threading.Thread):
+    current_uuid = None
+
+    def __init__(self, q, notification_q, app, datastore, *args, **kwargs):
+        self.q = q
+        self.app = app
+        self.notification_q = notification_q
+        self.datastore = datastore
+        super().__init__(*args, **kwargs)
+
+    def run(self):
+        from backend import fetch_site_status
+
+        update_handler = fetch_site_status.perform_site_check(datastore=self.datastore)
+
+        while not self.app.config.exit.is_set():
+
+            try:
+                uuid = self.q.get(block=False)
+            except queue.Empty:
+                pass
+
+            else:
+                self.current_uuid = uuid
+
+                if uuid in list(self.datastore.data['watching'].keys()):
+                    try:
+                        changed_detected, result, contents = update_handler.run(uuid)
+
+                    except PermissionError as s:
+                        self.app.logger.error("File permission error updating", uuid, str(s))
+                    else:
+                        if result:
+                            try:
+                                self.datastore.update_watch(uuid=uuid, update_obj=result)
+                                if changed_detected:
+                                    # A change was detected
+                                    self.datastore.save_history_text(uuid=uuid, contents=contents, result_obj=result)
+
+                                    watch = self.datastore.data['watching'][uuid]
+
+                                    # Did it have any notification alerts to hit?
+                                    if len(watch['notification_urls']):
+                                        print("Processing notifications for UUID: {}".format(uuid))
+                                        n_object = {'watch_url': self.datastore.data['watching'][uuid]['url'],
+                                                    'notification_urls': watch['notification_urls']}
+                                        self.notification_q.put(n_object)
+
+
+                                    # No? maybe theres a global setting, queue them all
+                                    elif len(self.datastore.data['settings']['application']['notification_urls']):
+                                        print("Processing GLOBAL notifications for UUID: {}".format(uuid))
+                                        n_object = {'watch_url': self.datastore.data['watching'][uuid]['url'],
+                                                    'notification_urls': self.datastore.data['settings']['application'][
+                                                        'notification_urls']}
+                                        self.notification_q.put(n_object)
+                            except Exception as e:
+                                print("!!!! Exception in update_worker !!!\n", e)
+
+                self.current_uuid = None  # Done
+                self.q.task_done()
+
+            self.app.config.exit.wait(1)