Bump nox from 2020.12.31 to 2021.6.12 in /.github/workflows (#310)

* Bump nox from 2020.12.31 to 2021.6.12 in /.github/workflows

Bumps [nox](https://github.com/theacodes/nox) from 2020.12.31 to 2021.6.12.
- [Release notes](https://github.com/theacodes/nox/releases)
- [Changelog](https://github.com/theacodes/nox/blob/main/CHANGELOG.md)
- [Commits](wntrblm/nox@2020.12.31...2021.6.12)

---
updated-dependencies:
- dependency-name: nox
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

* Ignore unreachable

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: epenet <6771947+epenet@users.noreply.github.com>

.github/workflows/constraints.txt

@@ -1,5 +1,5 @@
 pip==21.2.1
-nox==2020.12.31
+nox==2021.6.12
 nox-poetry==0.8.6
 poetry==1.1.7
 virtualenv==20.6.0

noxfile.py

@@ -33,7 +33,7 @@ def activate_virtualenv_in_precommit_hooks(session: Session) -> None:
         session: The Session object.
     """
     if session.bin is None:
-        return
+        return  # type: ignore
 
     virtualenv = session.env.get("VIRTUAL_ENV")
     if virtualenv is None: