Add analysis-time deprecation warning

Summary:
let folks know when they're building things that will break when 3.8 goes away.

even if the person building is not the one who can upgrade, they would at least know and could reach out to the appropriate owners, in addition to the oncall task that already exists.

Reviewed By: lisroach

Differential Revision: D52589353

fbshipit-source-id: 0fd1e185c15fdaeba99f8fe1e3537df5efc47d49

Author: itamaro

prelude/python/python_binary.bzl

@@ -714,6 +714,19 @@ def python_binary_impl(ctx: AnalysisContext) -> list[Provider]:
         if main_module.endswith(".py"):
             main_module = main_module[:-3]
 
+    if "python-version=3.8" in ctx.attrs.labels:
+        # buildifier: disable=print
+        print((
+            "\033[1;33m \u26A0  " +
+            "{0} 3.8 is EOL, and is going away by the end of H1 2024. " +
+            "Upgrade //{1}:{2} to {0} 3.10 now to avoid breakages. " +
+            "https://fburl.com/py38-sunsetting \033[0m"
+        ).format(
+            "Cinder" if "python-flavor=cinder" in ctx.attrs.labels else "Python",
+            ctx.label.package,
+            ctx.attrs.name,
+        ))
+
     if main_module != None:
         main = (EntryPointKind("module"), main_module)
     else: