Do not load system certificates when `certifi` is used

This causes `CERTIFICATE_VERIFY_FAILED` if there is an
expired/bad certificate in the system store

Partially reverts 8a82af3511b4379af0d239dbd01c672c17a2c46a

Related: #4145

README.md

@@ -146,8 +146,8 @@ Some of yt-dlp's default options are different from that of youtube-dl and youtu
 * Thumbnail embedding in `mp4` is done with mutagen if possible. Use `--compat-options embed-thumbnail-atomicparsley` to force the use of AtomicParsley instead
 * Some private fields such as filenames are removed by default from the infojson. Use `--no-clean-infojson` or `--compat-options no-clean-infojson` to revert this
 * When `--embed-subs` and `--write-subs` are used together, the subtitles are written to disk and also embedded in the media file. You can use just `--embed-subs` to embed the subs and automatically delete the separate file. See [#630 (comment)](https://github.com/yt-dlp/yt-dlp/issues/630#issuecomment-893659460) for more info. `--compat-options no-keep-subs` can be used to revert this
-* `certifi` will be used for SSL root certificates, if installed. If you want to use only system certificates, use `--compat-options no-certifi`
-* youtube-dl tries to remove some superfluous punctuations from filenames. While this can sometimes be helpful, it is often undesirable. So yt-dlp tries to keep the fields in the filenames as close to their original values as possible. You can use `--compat-options filename-sanitization` to revert to youtube-dl's behavior
+* `certifi` will be used for SSL root certificates, if installed. If you want to use system certificates (e.g. self-signed), use `--compat-options no-certifi`
+* youtube-dl tries to remove some superfluous punctuations from filenames. While this can sometimes be helpfull, it is often undesirable. So yt-dlp tries to keep the fields in the filenames as close to their original values as possible. You can use `--compat-options filename-sanitization` to revert to youtube-dl's behavior
 
 For ease of use, a few more compat options are available:
 

yt_dlp/utils.py

@@ -950,17 +950,18 @@ def make_HTTPS_handler(params, **kwargs):
     if opts_check_certificate:
         if has_certifi and 'no-certifi' not in params.get('compat_opts', []):
             context.load_verify_locations(cafile=certifi.where())
-        try:
-            context.load_default_certs()
-        # Work around the issue in load_default_certs when there are bad certificates. See:
-        # https://github.com/yt-dlp/yt-dlp/issues/1060,
-        # https://bugs.python.org/issue35665, https://bugs.python.org/issue45312
-        except ssl.SSLError:
-            # enum_certificates is not present in mingw python. See https://github.com/yt-dlp/yt-dlp/issues/1151
-            if sys.platform == 'win32' and hasattr(ssl, 'enum_certificates'):
-                for storename in ('CA', 'ROOT'):
-                    _ssl_load_windows_store_certs(context, storename)
-            context.set_default_verify_paths()
+        else:
+            try:
+                context.load_default_certs()
+                # Work around the issue in load_default_certs when there are bad certificates. See:
+                # https://github.com/yt-dlp/yt-dlp/issues/1060,
+                # https://bugs.python.org/issue35665, https://bugs.python.org/issue45312
+            except ssl.SSLError:
+                # enum_certificates is not present in mingw python. See https://github.com/yt-dlp/yt-dlp/issues/1151
+                if sys.platform == 'win32' and hasattr(ssl, 'enum_certificates'):
+                    for storename in ('CA', 'ROOT'):
+                        _ssl_load_windows_store_certs(context, storename)
+                context.set_default_verify_paths()
 
     client_certfile = params.get('client_certificate')
     if client_certfile: