Add Reno to Riot (DataDog#2931)

* Added a venv for reno in the riotfile. Documented the use of reno to create release notes, for contributors

* ran riot run fmt

Co-authored-by: Gabriele N. Tornetta <P403n1x87@users.noreply.github.com>

README.md

@@ -147,3 +147,14 @@ the CLI can be found at https://circleci.com/docs/2.0/local-cli/.
 After installing the `circleci` CLI, you can run jobs by name. For example:
 
     $ circleci build --job django
+
+### Release Notes
+
+This project follows [semver](https://semver.org/) and so bug fixes, breaking
+changes, new features, etc must be accompanied by a release note. To generate a
+release note:
+
+    $ riot run reno new <short-description-of-change>
+
+Document the changes in the generated file, remove the irrelevant sections and
+commit the release note with the change.

riotfile.py

@@ -1252,5 +1252,13 @@ def select_pys(min_version=MIN_PYTHON_VERSION, max_version=MAX_PYTHON_VERSION):
                 ),
             ],
         ),
+        Venv(
+            pys=["3"],
+            name="reno",
+            pkgs={
+                "reno": latest,
+            },
+            command="reno {cmdargs}",
+        ),
     ],
 )