Unbreak unit tests with Twisted 25.5.0 by add parsePOSTFormSubmission arg to FakeSite (#18577)

Co-authored-by: anoa's Codex Agent <codex@amorgan.xyz>

tests/server.py

@@ -343,6 +343,8 @@ class FakeSite:
         self,
         resource: IResource,
         reactor: IReactorTime,
+        *,
+        parsePOSTFormSubmission: bool = True,
     ):
         """
 
@@ -351,6 +353,7 @@ class FakeSite:
         """
         self._resource = resource
         self.reactor = reactor
+        self._parsePOSTFormSubmission = parsePOSTFormSubmission
 
     def getResourceFor(self, request: Request) -> IResource:
         return self._resource
@@ -514,9 +517,13 @@ class ThreadedMemoryReactorClock(MemoryReactorClock):
 
             tls._get_default_clock = lambda: self
 
-        self.nameResolver = SimpleResolverComplexifier(FakeResolver())
         super().__init__()
 
+        # Override the default name resolver with our fake resolver. This must
+        # happen after `super().__init__()` so that the base class doesn't
+        # overwrite it again.
+        self.nameResolver = SimpleResolverComplexifier(FakeResolver())
+
     def installNameResolver(self, resolver: IHostnameResolver) -> IHostnameResolver:
         raise NotImplementedError()