Added the APscheduler 3.9.1 source into the Linspector source tree.

apscheduler/schedulers/__init__.py

@@ -0,0 +1,12 @@
+class SchedulerAlreadyRunningError(Exception):
+    """Raised when attempting to start or configure the scheduler when it's already running."""
+
+    def __str__(self):
+        return 'Scheduler is already running'
+
+
+class SchedulerNotRunningError(Exception):
+    """Raised when attempting to shutdown the scheduler when it's not running."""
+
+    def __str__(self):
+        return 'Scheduler is not running'