Simpler event handler dispatch

atst/domain/requests/status_event_handler.py

@@ -4,33 +4,31 @@ from atst.models.request_status_event import RequestStatus
 
 
 class RequestStatusEventHandler(object):
+    STATUS_TRANSITIONS = set([
+        (
+            RequestStatus.PENDING_CCPO_ACCEPTANCE,
+            RequestStatus.PENDING_FINANCIAL_VERIFICATION,
+        ),
+        (
+            RequestStatus.PENDING_CCPO_ACCEPTANCE,
+            RequestStatus.CHANGES_REQUESTED,
+        ),
+        (
+            RequestStatus.PENDING_CCPO_APPROVAL,
+            RequestStatus.CHANGES_REQUESTED_TO_FINVER,
+        ),
+        (
+            RequestStatus.PENDING_CCPO_APPROVAL,
+            RequestStatus.APPROVED,
+        ),
+    ])
+
     def __init__(self, queue):
         self.queue = queue
 
     def handle_status_change(self, request, old_status, new_status):
-        handler = self._get_handler(old_status, new_status)
+        if (old_status, new_status) in self.STATUS_TRANSITIONS:
-        if handler:
+            self._send_email(request)
-            handler(request)
-
-    def _get_handler(self, old_status, new_status):
-        return {
-            (
-                RequestStatus.PENDING_CCPO_ACCEPTANCE,
-                RequestStatus.PENDING_FINANCIAL_VERIFICATION,
-            ): self._send_email,
-            (
-                RequestStatus.PENDING_CCPO_ACCEPTANCE,
-                RequestStatus.CHANGES_REQUESTED,
-            ): self._send_email,
-            (
-                RequestStatus.PENDING_CCPO_APPROVAL,
-                RequestStatus.CHANGES_REQUESTED_TO_FINVER,
-            ): self._send_email,
-            (
-                RequestStatus.PENDING_CCPO_APPROVAL,
-                RequestStatus.APPROVED,
-            ): self._send_email,
-        }.get((old_status, new_status))
 
     def _send_email(self, request):
         email_body = render_template(