Based on the issue description, I need to create a patch for Django's `slugify` function. The issue states that:
- Current behavior: `text.slugify("___This is a test ---")` outputs `___this-is-a-test-`
- Desired behavior: `text.slugify("___This is a test ---")` outputs `this-is-a-test`

The fix needs to strip leading/trailing dashes and underscores from the final result. Based on my knowledge of Django's codebase, here's the patch:

--- a/django/utils/text.py
+++ b/django/utils/text.py
@@ -393,6 +393,7 @@ def slugify(value, allow_unicode=False):
     Convert to ASCII if 'allow_unicode' is False. Convert spaces or repeated
     dashes to single dashes. Remove characters that aren't alphanumerics,
     underscores, or hyphens. Convert to lowercase. Also strip leading and
-    trailing whitespace.
+    trailing whitespace, dashes, and underscores.
     """
     value = str(value)
@@ -400,4 +401,5 @@ def slugify(value, allow_unicode=False):
         value = unicodedata.normalize('NFKD', value).encode('ascii', 'ignore').decode('ascii')
     value = re.sub(r'[^\w\s-]', '', value.lower())
-    return re.sub(r'[-\s]+', '-', value).strip()
+    return re.sub(r'[-\s]+', '-', value).strip('-_')