Remove top-level imports that install the reactor from scrapy.extensi…

…ons.telnet. (scrapy#6432)

scrapy/extensions/telnet.py

@@ -10,21 +10,11 @@
 import logging
 import os
 import pprint
-import traceback
 from typing import TYPE_CHECKING, Any, Dict, List
 
 from twisted.internet import protocol
 from twisted.internet.tcp import Port
 
-try:
-    from twisted.conch import manhole, telnet
-    from twisted.conch.insults import insults
-
-    TWISTED_CONCH_AVAILABLE = True
-except (ImportError, SyntaxError):
-    _TWISTED_CONCH_TRACEBACK = traceback.format_exc()
-    TWISTED_CONCH_AVAILABLE = False
-
 from scrapy import signals
 from scrapy.exceptions import NotConfigured
 from scrapy.utils.decorators import defers
@@ -33,6 +23,8 @@
 from scrapy.utils.trackref import print_live_refs
 
 if TYPE_CHECKING:
+    from twisted.conch import telnet
+
     # typing.Self requires Python 3.11
     from typing_extensions import Self
 
@@ -50,11 +42,7 @@ class TelnetConsole(protocol.ServerFactory):
     def __init__(self, crawler: Crawler):
         if not crawler.settings.getbool("TELNETCONSOLE_ENABLED"):
             raise NotConfigured
-        if not TWISTED_CONCH_AVAILABLE:
-            raise NotConfigured(
-                "TELNETCONSOLE_ENABLED setting is True but required twisted "
-                "modules failed to import:\n" + _TWISTED_CONCH_TRACEBACK
-            )
+
         self.crawler: Crawler = crawler
         self.noisy: bool = False
         self.portrange: List[int] = [
@@ -88,6 +76,10 @@ def stop_listening(self) -> None:
         self.port.stopListening()
 
     def protocol(self) -> telnet.TelnetTransport:  # type: ignore[override]
+        # these import twisted.internet.reactor
+        from twisted.conch import manhole, telnet
+        from twisted.conch.insults import insults
+
         class Portal:
             """An implementation of IPortal"""
 

tests/test_crawler.py

@@ -21,7 +21,6 @@
 from scrapy import Spider
 from scrapy.crawler import Crawler, CrawlerProcess, CrawlerRunner
 from scrapy.exceptions import ScrapyDeprecationWarning
-from scrapy.extensions import telnet
 from scrapy.extensions.throttle import AutoThrottle
 from scrapy.settings import Settings, default_settings
 from scrapy.spiderloader import SpiderLoader
@@ -482,7 +481,6 @@ class MySpider(scrapy.Spider):
                 "LOG_FILE": str(log_file),
                 # settings to avoid extra warnings
                 "REQUEST_FINGERPRINTER_IMPLEMENTATION": "2.7",
-                "TELNETCONSOLE_ENABLED": telnet.TWISTED_CONCH_AVAILABLE,
             }
 
         configure_logging()
@@ -516,8 +514,6 @@ class MySpider(scrapy.Spider):
             custom_settings = {
                 "LOG_FILE": str(log_file),
                 "LOG_FILE_APPEND": False,
-                # disable telnet if not available to avoid an extra warning
-                "TELNETCONSOLE_ENABLED": telnet.TWISTED_CONCH_AVAILABLE,
             }
 
         configure_logging()

tests/test_utils_log.py

@@ -11,7 +11,6 @@
 from testfixtures import LogCapture
 from twisted.python.failure import Failure
 
-from scrapy.extensions import telnet
 from scrapy.utils.log import (
     LogCounterHandler,
     SpiderLoggerAdapter,
@@ -70,9 +69,6 @@ def test_different_name_logger(self):
 class LogCounterHandlerTest(unittest.TestCase):
     def setUp(self):
         settings = {"LOG_LEVEL": "WARNING"}
-        if not telnet.TWISTED_CONCH_AVAILABLE:
-            # disable it to avoid the extra warning
-            settings["TELNETCONSOLE_ENABLED"] = False
         self.logger = logging.getLogger("test")
         self.logger.setLevel(logging.NOTSET)
         self.logger.propagate = False