Update 2.7 deprecation message (#6726)

docs/html/development/release-process.rst

@@ -57,6 +57,21 @@ their merits.
   ``pip._internal.utils.deprecation.deprecated``. The function is not a part of
   pip's public API.
 
+Python 2 support
+----------------
+
+pip will continue to ensure that it runs on Python 2.7 after the CPython 2.7
+EOL date. Support for Python 2.7 will be dropped, if bugs in Python 2.7 itself
+make this necessary (which is unlikely) or Python 2 usage reduces to a level
+where pip maintainers feel it is OK to drop support. The same approach is used
+to determine when to drop support for other Python versions.
+
+However, bugs reported with pip which only occur on Python 2.7 would likely not
+be addressed directly by pip's maintainers. Pull Requests to fix Python 2.7
+only bugs will be considered, and merged (subject to normal review processes).
+Note that there may be delays due to the lack of developer resources for
+reviewing such pull requests.
+
 
 Release Process
 ===============

news/6726.doc

@@ -0,0 +1 @@
+Document how Python 2.7 support will be maintained.

src/pip/_internal/cli/base_command.py

@@ -154,7 +154,9 @@ def main(self, args):
 
         if sys.version_info[:2] == (2, 7):
             message = (
-                "A future version of pip will drop support for Python 2.7."
+                "A future version of pip will drop support for Python 2.7. "
+                "More details about Python 2 support in pip, can be found at "
+                "https://pip.pypa.io/en/latest/development/release-process/#python-2-support"  # noqa
             )
             if platform.python_implementation() == "CPython":
                 message = (