Remove vendored html5lib.

Author: sbidoul

news/html5lib.vendor.rst

@@ -0,0 +1 @@
+Remove vendored html5lib.

src/pip/_vendor/README.rst

@@ -104,9 +104,6 @@ Modifications
   rather than ``appdirs``.
 * ``packaging`` has been modified to import its dependencies from
   ``pip._vendor``.
-* ``html5lib`` has been modified to import six from ``pip._vendor``, to prefer
-  importing from ``collections.abc`` instead of ``collections`` and does not
-  import ``xml.etree.cElementTree`` on Python 3.
 * ``CacheControl`` has been modified to import its dependencies from
   ``pip._vendor``.
 * ``requests`` has been modified to import its other dependencies from

src/pip/_vendor/__init__.py

@@ -63,7 +63,6 @@ def vendored(modulename):
     vendored("colorama")
     vendored("distlib")
     vendored("distro")
-    vendored("html5lib")
     vendored("six")
     vendored("six.moves")
     vendored("six.moves.urllib")