diff --git a/bootstrap.py b/bootstrap.py
new file mode 100644
index 0000000000..229b996503
--- /dev/null
+++ b/bootstrap.py
@@ -0,0 +1,7 @@
+import warnings
+
+
+msg = "bootstrap.py is no longer needed. Use a PEP-517-compatible builder instead."
+
+
+__name__ == '__main__' and warnings.warn(msg)