Force install tox>=4 for Python 3.7

noxfile.py

@@ -37,6 +37,15 @@ def tests(session: nox.Session) -> None:
     session.create_tmp()  # Fixes permission errors on Windows
     session.install("-r", "requirements-test.txt")
     session.install("-e", ".[tox_to_nox]")
+    if session.python == "3.7":
+        # Force reinstall tox to version 4+
+        # This is needed for Python 3.7 because there is
+        # a dependency conflict between argcomplete and
+        # the latest tox (both depend on a different
+        # version of importlib-metadata for Py 3.7)
+        # and if we just let pip install the latest version
+        # of tox, it installs tox 3 because then all deps match.
+        session.install("tox>=4")
     session.run(
         "pytest",
         "--cov=nox",