From a29dda6d2b1d0b1c5566438a2f0377ca11ee9442 Mon Sep 17 00:00:00 2001
From: Noah Gorny <noah@gittabags.com>
Date: Sat, 14 Nov 2020 12:03:53 +0200
Subject: [PATCH 1/2] cli: Drop --unstable-feature flag

---
 src/pip/_internal/cli/base_command.py |  7 -------
 src/pip/_internal/cli/cmdoptions.py   | 12 ------------
 2 files changed, 19 deletions(-)

diff --git a/src/pip/_internal/cli/base_command.py b/src/pip/_internal/cli/base_command.py
index 86f1733a5..c1522d639 100644
--- a/src/pip/_internal/cli/base_command.py
+++ b/src/pip/_internal/cli/base_command.py
@@ -199,13 +199,6 @@ class Command(CommandContextMixIn):
                 )
                 options.cache_dir = None
 
-        if 'resolver' in options.unstable_features:
-            logger.critical(
-                "--unstable-feature=resolver is no longer supported, and "
-                "has been replaced with --use-feature=2020-resolver instead."
-            )
-            sys.exit(ERROR)
-
         if '2020-resolver' in options.features_enabled and not PY2:
             logger.warning(
                 "--use-feature=2020-resolver no longer has any effect, "
diff --git a/src/pip/_internal/cli/cmdoptions.py b/src/pip/_internal/cli/cmdoptions.py
index 6a6634fb8..07d612a6f 100644
--- a/src/pip/_internal/cli/cmdoptions.py
+++ b/src/pip/_internal/cli/cmdoptions.py
@@ -895,17 +895,6 @@ no_python_version_warning = partial(
 )  # type: Callable[..., Option]
 
 
-unstable_feature = partial(
-    Option,
-    '--unstable-feature',
-    dest='unstable_features',
-    metavar='feature',
-    action='append',
-    default=[],
-    choices=['resolver'],
-    help=SUPPRESS_HELP,  # TODO: drop this in pip 20.3
-)  # type: Callable[..., Option]
-
 use_new_feature = partial(
     Option,
     '--use-feature',
@@ -958,7 +947,6 @@ general_group = {
         disable_pip_version_check,
         no_color,
         no_python_version_warning,
-        unstable_feature,
         use_new_feature,
         use_deprecated_feature,
     ]

From 62868dca5faad557bd6f822b7c11faf3bc989140 Mon Sep 17 00:00:00 2001
From: Noah Gorny <noah@gittabags.com>
Date: Sat, 14 Nov 2020 12:08:17 +0200
Subject: [PATCH 2/2] news: Add --unstable-feature removal news fragment

---
 news/9133.removal.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 news/9133.removal.rst

diff --git a/news/9133.removal.rst b/news/9133.removal.rst
new file mode 100644
index 000000000..876e89b13
--- /dev/null
+++ b/news/9133.removal.rst
@@ -0,0 +1 @@
+Remove --unstable-feature flag as it has been deprecated.