Use a different warning class so users get warnings (#4014)
* Use a different warning class so users get warnings
* fixed tests
* do our own warning class
* typo
* flake8
diff --git a/docs/api-stability.rst b/docs/api-stability.rst
index 7ba1d42..2bb5384 100644
--- a/docs/api-stability.rst
+++ b/docs/api-stability.rst
@@ -42,9 +42,9 @@
* In ``cryptography X.Y`` the feature exists.
* In ``cryptography X.Y+1`` using that feature will emit a
- ``PendingDeprecationWarning``.
+ ``UserWarning``.
* In ``cryptography X.Y+2`` using that feature will emit a
- ``DeprecationWarning``.
+ ``UserWarning``.
* In ``cryptography X.Y+3`` the feature will be removed or changed.
In short, code that runs without warnings will always continue to work for a