Don't load plugins by default

devscripts/run_tests.py

@@ -51,7 +51,7 @@ def run_tests(*tests, pattern=None, ci=False, load_plugins=False):
     try:
         return subprocess.call(arguments, env={
             **os.environ,
-            'YTDLP_NO_PLUGINS': '1' if os.environ.get('YTDLP_NO_PLUGINS') or not load_plugins else '',
+            '_YT_DLP_TEST_DO_LOAD_PLUGINS': '1' if load_plugins else '',
         })
     except FileNotFoundError:
         pass

test/helper.py

@@ -1,6 +1,7 @@
 import errno
 import hashlib
 import json
+import os
 import os.path
 import re
 import ssl
@@ -87,8 +88,9 @@ class FakeYDL(YoutubeDL):
 
 
 def gettestcases(include_onlymatching=False):
-    import yt_dlp.plugins
+    if os.environ.get('_YT_DLP_TEST_DO_LOAD_PLUGINS'):
-    yt_dlp.plugins.load_all_plugins()
+        import yt_dlp.plugins as plugins
+        plugins.load_all_plugins()
     for ie in yt_dlp.extractor.gen_extractors():
         yield from ie.get_testcases(include_onlymatching)