Remove Python 3.6 support

Closes #3764

yt_dlp/compat/__init__.py

@@ -3,13 +3,12 @@
 import warnings
 import xml.etree.ElementTree as etree
 
-from . import re
 from ._deprecated import *  # noqa: F401, F403
 from .compat_utils import passthrough_module
 
 # XXX: Implement this the same way as other DeprecationWarnings without circular import
 passthrough_module(__name__, '._legacy', callback=lambda attr: warnings.warn(
-    DeprecationWarning(f'{__name__}.{attr} is deprecated'), stacklevel=2))
+    DeprecationWarning(f'{__name__}.{attr} is deprecated'), stacklevel=3))
 
 
 # HTMLParseError has been deprecated in Python 3.3 and removed in
@@ -33,6 +32,7 @@ def compat_etree_fromstring(text):
 
 if compat_os_name == 'nt':
     def compat_shlex_quote(s):
+        import re
         return s if re.match(r'^[-_\w./]+$', s) else '"%s"' % s.replace('"', '\\"')
 else:
     from shlex import quote as compat_shlex_quote  # noqa: F401

yt_dlp/compat/_legacy.py

@@ -22,10 +22,14 @@
 import xml.etree.ElementTree as etree
 from subprocess import DEVNULL
 
-from .compat_utils import passthrough_module  # isort: split
-from .asyncio import run as compat_asyncio_run  # noqa: F401
-from .re import Pattern as compat_Pattern  # noqa: F401
-from .re import match as compat_Match  # noqa: F401
+# isort: split
+import asyncio  # noqa: F401
+import re  # noqa: F401
+from asyncio import run as compat_asyncio_run  # noqa: F401
+from re import Pattern as compat_Pattern  # noqa: F401
+from re import match as compat_Match  # noqa: F401
+
+from .compat_utils import passthrough_module
 from ..dependencies import Cryptodome_AES as compat_pycrypto_AES  # noqa: F401
 from ..dependencies import brotli as compat_brotli  # noqa: F401
 from ..dependencies import websockets as compat_websockets  # noqa: F401

yt_dlp/compat/asyncio.py

@@ -1,23 +0,0 @@
-# flake8: noqa: F405
-from asyncio import *  # noqa: F403
-
-from .compat_utils import passthrough_module
-
-passthrough_module(__name__, 'asyncio')
-del passthrough_module
-
-try:
-    run  # >= 3.7
-except NameError:
-    def run(coro):
-        try:
-            loop = get_event_loop()
-        except RuntimeError:
-            loop = new_event_loop()
-            set_event_loop(loop)
-        loop.run_until_complete(coro)
-
-try:
-    all_tasks  # >= 3.7
-except NameError:
-    all_tasks = Task.all_tasks

yt_dlp/compat/re.py

@@ -1,18 +0,0 @@
-# flake8: noqa: F405
-from re import *  # F403
-
-from .compat_utils import passthrough_module
-
-passthrough_module(__name__, 're')
-del passthrough_module
-
-try:
-    Pattern  # >= 3.7
-except NameError:
-    Pattern = type(compile(''))
-
-
-try:
-    Match  # >= 3.7
-except NameError:
-    Match = type(compile('').match(''))