Add PyCapsule API

CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Add `Py::setattr` method. [#2009](https://github.com/PyO3/pyo3/pull/2009)
+- Add `PyCapsule`, exposing the [Capsule API](https://docs.python.org/3/c-api/capsule.html#capsules). [#1980](https://github.com/PyO3/pyo3/pull/1980)
 
 ### Changed
 

src/lib.rs

@@ -334,6 +334,7 @@ pub mod marshal;
 pub mod once_cell;
 pub mod panic;
 pub mod prelude;
+pub mod pycapsule;
 pub mod pycell;
 pub mod pyclass;
 pub mod pyclass_init;