Fix build pipeline failures related to mypy & black

Author: renoyjohnm

tableauserverclient/server/request_factory.py

@@ -1118,14 +1118,17 @@ def run_req(self, xml_request: ET.Element, task_item: Any) -> None:
         pass
 
     @_tsrequest_wrapped
-    def refresh_req(self, xml_request: ET.Element, incremental: bool = False, parent_srv: Optional["Server"] = None) -> bytes:
+    def refresh_req(
+        self, xml_request: ET.Element, incremental: bool = False, parent_srv: Optional["Server"] = None
+    ) -> Optional[bytes]:
         if parent_srv is not None and parent_srv.check_at_least_version("3.25"):
             task_element = ET.SubElement(xml_request, "extractRefresh")
             if incremental:
                 task_element.attrib["incremental"] = "true"
             return ET.tostring(xml_request)
         elif incremental:
             raise ValueError("Incremental refresh is only supported in 3.25+")
+        return None
 
     @_tsrequest_wrapped
     def create_extract_req(self, xml_request: ET.Element, extract_item: "TaskItem") -> bytes:

test/request_factory/test_task_requests.py

@@ -3,6 +3,7 @@
 from unittest.mock import Mock
 from tableauserverclient.server.request_factory import TaskRequest
 
+
 class TestTaskRequest(unittest.TestCase):
 
     def setUp(self):