zproject: Prevent having exactly 17/18 middlewares, for Python 3.11 bug.

Having exactly 17 or 18 middlewares, on Python 3.11.0 and above,
causes python to segfault when running tests with coverage; see
python/cpython#106092

Work around this by adding a no-op middleware if we would hit that
unlucky number.  We only add it in testing, since coverage is a
requirement to trigger it, and there is no reason to burden production
with an additional wrapping.

zerver/middleware.py

@@ -689,3 +689,7 @@ def process_request(self, request: HttpRequest) -> Optional[HttpResponse]:
             return response
 
         return None
+
+
+class ZulipNoopMiddleware(MiddlewareMixin):
+    pass

zproject/computed_settings.py

@@ -159,7 +159,7 @@
 # ... and with the hosts in REALM_HOSTS.
 ALLOWED_HOSTS += REALM_HOSTS.values()
 
-MIDDLEWARE = (
+MIDDLEWARE = [
     "zerver.middleware.TagRequests",
     "zerver.middleware.SetRemoteAddrFromRealIpHeader",
     "zerver.middleware.RequestContext",
@@ -182,7 +182,7 @@
     "two_factor.middleware.threadlocals.ThreadLocals",  # Required by Twilio
     # Needs to be after CommonMiddleware, which sets Content-Length
     "zerver.middleware.FinalizeOpenGraphDescription",
-)
+]
 
 AUTH_USER_MODEL = "zerver.UserProfile"
 

zproject/test_extra_settings.py

@@ -15,6 +15,7 @@
     EXTERNAL_HOST,
     LOCAL_DATABASE_PASSWORD,
     LOGGING,
+    MIDDLEWARE,
 )
 
 FULL_STACK_ZULIP_TEST = "FULL_STACK_ZULIP_TEST" in os.environ
@@ -269,3 +270,13 @@ def set_loglevel(logger_name: str, level: str) -> None:
         "name_formatted_included": True,
     }
 }
+
+
+while len(MIDDLEWARE) < 19:
+    # The following middleware serves to skip having exactly 17 or 18
+    # middlewares, which can segfault Python 3.11 when running with
+    # coverage enabled; see
+    # https://github.com/python/cpython/issues/106092
+    MIDDLEWARE += [
+        "zerver.middleware.ZulipNoopMiddleware",
+    ]