session.install for lint

Install current `packaging` and its dependencies during lint.
`nox` depends on `packaging`, by installing `nox` during lint phase,
`packaging` dependencies defined in working branch are overridden by
latest `packaging` release dependencies.
In this case, since the PR changes the constraints on `pyparsing`,
without a `session.install(".")` the incorrect `pyparsing` version will
be installed.

noxfile.py

@@ -59,6 +59,9 @@ def lint(session):
     session.install("pre-commit")
     session.run("pre-commit", "run", "--all-files")
 
+    # Install current package and dependencies
+    session.install(".")
+
     # Check the distribution
     session.install("build", "twine")
     session.run("python", "-m", "build")