spack style: fix isort on sl:7

fixes spack#41096

Bump the minimum version required for isort. This should fix
an issue reported on Scientific Linux 7, and due to:

PyCQA/isort#1363

lib/spack/spack/bootstrap/environment.py

@@ -161,7 +161,7 @@ def _write_spack_yaml_file(self) -> None:
 
 def isort_root_spec() -> str:
     """Return the root spec used to bootstrap isort"""
-    return _root_spec("py-isort@4.3.5:")
+    return _root_spec("py-isort@5")
 
 
 def mypy_root_spec() -> str:

var/spack/repos/builtin/packages/py-isort/package.py

@@ -16,13 +16,23 @@ class PyIsort(PythonPackage):
     version("5.10.1", sha256="e8443a5e7a020e9d7f97f1d7d9cd17c88bcb3bc7e218bf9cf5095fe550be2951")
     version("5.9.3", sha256="9c2ea1e62d871267b78307fe511c0838ba0da28698c5732d54e2790bf3ba9899")
     version("5.9.1", sha256="83510593e07e433b77bd5bff0f6f607dbafa06d1a89022616f02d8b699cfcd56")
-    version("4.3.20", sha256="c40744b6bc5162bbb39c1257fe298b7a393861d50978b565f3ccd9cb9de0182a")
-    version("4.2.15", sha256="79f46172d3a4e2e53e7016e663cc7a8b538bec525c36675fcfd2767df30b3983")
+    version(
+        "4.3.20",
+        sha256="c40744b6bc5162bbb39c1257fe298b7a393861d50978b565f3ccd9cb9de0182a",
+        deprecated=True,
+    )
+    version(
+        "4.2.15",
+        sha256="79f46172d3a4e2e53e7016e663cc7a8b538bec525c36675fcfd2767df30b3983",
+        deprecated=True,
+    )
 
     variant("colors", default=False, description="Install colorama for --color support")
 
     depends_on("python@3.8:", when="@5.12:", type=("build", "run"))
-    depends_on("python@3.6.1:3", when="@5:5.10", type=("build", "run"))
+    # This needs to be @3.6 since for bootstrapping the current Spack interpreter is
+    # identified by major.minor (and the new versioning identifies it as @=3.6)
+    depends_on("python@3.6", when="@5:5.10", type=("build", "run"))
     depends_on("py-setuptools", when="@:4", type=("build", "run"))
     depends_on("py-poetry-core@1:", when="@5:", type="build")
     depends_on("py-colorama@0.4.3:", when="+colors @5.12:", type=("build", "run"))