refactor: rework deprecation of get-poetry.py to include CI brownout and restructured messaging

get-poetry.py

@@ -21,6 +21,7 @@ import hashlib
 import json
 import os
 import platform
+import random
 import re
 import shutil
 import stat
@@ -69,6 +70,8 @@ SHELL = os.getenv("SHELL", "")
 WINDOWS = sys.platform.startswith("win") or (sys.platform == "cli" and os.name == "nt")
 
 
+BROWNOUT_CHANCE = 5  # percent chance to randomly fail in CI
+
 FOREGROUND_COLORS = {
     "black": 30,
     "red": 31,
@@ -118,6 +121,7 @@ STYLES = {
     "comment": style("yellow", None, None),
     "error": style("red", None, None),
     "warning": style("yellow", None, None),
+    "deprecation": style("magenta", None, None),
 }
 
 
@@ -437,6 +441,58 @@ class Installer:
 
             return None, None
 
+        def _is_supported(x):
+            mx = self.VERSION_REGEX.match(x)
+            vx = tuple(int(p) for p in mx.groups()[:3]) + (mx.group(5),)
+            return vx < (1, 2, 0)
+
+        print(
+            colorize(
+                "deprecation",
+                "This installer is deprecated, and cannot install Poetry 1.2.0a1 or"
+                " newer.\nAdditionally, Poetry installations created by this installer"
+                " cannot `self update` to 1.2.0a1 or later.\nYou should migrate to"
+                " https://install.python-poetry.org instead. Instructions are available"
+                " at https://python-poetry.org/docs/#installation.\n",
+            )
+        )
+
+        if not os.environ.get("GET_POETRY_IGNORE_DEPRECATION"):
+            if os.environ.get("CI"):
+                print(
+                    colorize(
+                        "deprecation",
+                        "A CI environment has been detected! Due to the above"
+                        " deprecation, this installer is subject to an escalating"
+                        " brownout percentage (currently {percent}%)!\nIf you"
+                        " understand the above warning and wish to opt out of this"
+                        " brownout, set GET_POETRY_IGNORE_DEPRECATION=1 in the"
+                        " environment.\n".format(percent=BROWNOUT_CHANCE),
+                    )
+                )
+                if random.randrange(1, 100) < BROWNOUT_CHANCE:
+                    print(
+                        colorize(
+                            "error",
+                            "This invocation of the installer has been terminated due"
+                            " to the brownout described above. Please carefully read"
+                            " the above notices and update your CI pipeline"
+                            " accordingly!",
+                        )
+                    )
+                    return None, None
+            else:
+                print(
+                    colorize(
+                        "error",
+                        "This installer will now exit. If you understand the above"
+                        " warning and wish to proceed anyway, set"
+                        " GET_POETRY_IGNORE_DEPRECATION=1 in the environment and run"
+                        " this installer again.",
+                    )
+                )
+                return None, None
+
         version = self._version
         if not version:
             for release in reversed(releases):
@@ -444,39 +500,42 @@ class Installer:
                 if m.group(5) and not self.allows_prereleases():
                     continue
 
-                version = release
-
-                break
+                if _is_supported(release):
+                    version = release
+
+                    print(
+                        colorize(
+                            "warning",
+                            "Version {version} will be installed as it is the latest"
+                            " version supported by this installer.\nThis is not the"
+                            " latest version of Poetry! If you wish to install the"
+                            " latest version, please migrate to the new installer as"
+                            " described above!\n".format(version=release),
+                        )
+                    )
 
-        def _is_supported(x):
-            mx = self.VERSION_REGEX.match(x)
-            vx = tuple(int(p) for p in mx.groups()[:3]) + (mx.group(5),)
-            return vx < (1, 2, 0)
+                    break
+                else:
+                    print(
+                        colorize(
+                            "warning",
+                            "Version {version} is available but is not supported by"
+                            " this installer!".format(version=release),
+                        )
+                    )
 
         if not _is_supported(version):
             print(
                 colorize(
                     "error",
-                    "Version {version} does not support this installation method."
-                    " Please specify a version prior to 1.2.0a1 explicitly using the"
-                    " '--version' option.\nPlease see"
-                    " https://python-poetry.org/blog/announcing-poetry-1-2-0a1.html#deprecation-of-the-get-poetry-py-script"
-                    " for more information.".format(version=version),
+                    "Version {version} is not supported by this installer! Please"
+                    " specify a version prior to 1.2.0a1 to continue!".format(
+                        version=version
+                    ),
                 )
             )
             return None, None
 
-        print(
-            colorize(
-                "warning",
-                "This installer is deprecated. Poetry versions installed using this"
-                " script will not be able to use 'self update' command to upgrade to"
-                " 1.2.0a1 or later. It is recommended to use"
-                " https://install.python-poetry.org instead. Instructions are"
-                " available at https://python-poetry.org/docs/#installation",
-            )
-        )
-
         current_version = None
         if os.path.exists(POETRY_LIB):
             with open(