diff --git a/news/a1440b03-c0c6-4176-8e00-732517bed87b.trivial b/news/a1440b03-c0c6-4176-8e00-732517bed87b.trivial
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/src/pip/_vendor/README.rst b/src/pip/_vendor/README.rst
index d9e9b7f4081..8e9038ed760 100644
--- a/src/pip/_vendor/README.rst
+++ b/src/pip/_vendor/README.rst
@@ -146,3 +146,6 @@ extra work on your end in order to solve the problems described above.
 6. *(optional)* Update the ``pip_version_check`` logic to use the
    appropriate logic for determining the latest available version of pip and
    prompt the user with the correct upgrade message.
+
+Note that partial debundling is **NOT** supported. You need to prepare wheels
+for all dependencies for successful debundling.
diff --git a/src/pip/_vendor/__init__.py b/src/pip/_vendor/__init__.py
index b919b540d4d..c6f49c5cb9b 100644
--- a/src/pip/_vendor/__init__.py
+++ b/src/pip/_vendor/__init__.py
@@ -30,24 +30,21 @@ def vendored(modulename):
     vendored_name = "{0}.{1}".format(__name__, modulename)
 
     try:
-        __import__(vendored_name, globals(), locals(), level=0)
+        __import__(modulename, globals(), locals(), level=0)
     except ImportError:
-        try:
-            __import__(modulename, globals(), locals(), level=0)
-        except ImportError:
-            # We can just silently allow import failures to pass here. If we
-            # got to this point it means that ``import pip._vendor.whatever``
-            # failed and so did ``import whatever``. Since we're importing this
-            # upfront in an attempt to alias imports, not erroring here will
-            # just mean we get a regular import error whenever pip *actually*
-            # tries to import one of these modules to use it, which actually
-            # gives us a better error message than we would have otherwise
-            # gotten.
-            pass
-        else:
-            sys.modules[vendored_name] = sys.modules[modulename]
-            base, head = vendored_name.rsplit(".", 1)
-            setattr(sys.modules[base], head, sys.modules[modulename])
+        # We can just silently allow import failures to pass here. If we
+        # got to this point it means that ``import pip._vendor.whatever``
+        # failed and so did ``import whatever``. Since we're importing this
+        # upfront in an attempt to alias imports, not erroring here will
+        # just mean we get a regular import error whenever pip *actually*
+        # tries to import one of these modules to use it, which actually
+        # gives us a better error message than we would have otherwise
+        # gotten.
+        pass
+    else:
+        sys.modules[vendored_name] = sys.modules[modulename]
+        base, head = vendored_name.rsplit(".", 1)
+        setattr(sys.modules[base], head, sys.modules[modulename])
 
 
 # If we're operating in a debundled setup, then we want to go ahead and trigger