Revert "Remove Python 3.6 support"

This reverts commit 6929b41a21.

yt_dlp/compat/__init__.py

@@ -3,6 +3,7 @@ import sys
 import warnings
 import xml.etree.ElementTree as etree
 
+from . import re
 from ._deprecated import *  # noqa: F401, F403
 from .compat_utils import passthrough_module
 
@@ -32,7 +33,6 @@ compat_os_name = os._name if os.name == 'java' else os.name
 
 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