Use flake8-import-order to enforce PEP-8 compliance (#23947)

.flake8

@@ -66,6 +66,10 @@ exclude =
 
 format = spack
 
+# flake8-import-order settings
+application-import-names = llnl,spack
+import-order-style = pycharm
+
 [flake8:local-plugins]
 report =
   spack = flake8_formatter:SpackFormatter

.github/workflows/unit_tests.yaml

@@ -39,7 +39,7 @@ jobs:
         python-version: 3.9
     - name: Install Python packages
       run: |
-        pip install --upgrade pip six setuptools flake8 mypy>=0.800 black types-six types-python-dateutil
+        pip install --upgrade pip six setuptools flake8 flake8-import-order mypy>=0.800 black types-six types-python-dateutil
     - name: Setup git configuration
       run: |
         # Need this for the git tests to succeed.
@@ -370,7 +370,7 @@ jobs:
       run: |
           pip install --upgrade pip six setuptools
           pip install --upgrade codecov coverage
-          pip install --upgrade flake8 pep8-naming mypy
+          pip install --upgrade flake8 flake8-import-order pep8-naming mypy
           pip install --upgrade python-dateutil
     - name: Setup Homebrew packages
       run: |

lib/spack/spack/package.py

@@ -8,8 +8,8 @@
 The spack package class structure is based strongly on Homebrew
 (http://brew.sh/), mainly because Homebrew makes it very easy to create
 packages.
-
 """
+
 import base64
 import collections
 import contextlib
@@ -25,13 +25,14 @@
 import textwrap
 import time
 import traceback
-import six
 import types
-from typing import Optional, List, Dict, Any, Callable  # novm
+from typing import Any, Callable, Dict, List, Optional  # novm
+
+import six
+from ordereddict_backport import OrderedDict
 
 import llnl.util.filesystem as fsys
 import llnl.util.tty as tty
-
 import spack.compilers
 import spack.config
 import spack.dependency
@@ -51,14 +52,13 @@
 import spack.util.web
 from llnl.util.lang import memoized
 from llnl.util.link_tree import LinkTree
-from ordereddict_backport import OrderedDict
 from spack.filesystem_view import YamlFilesystemView
-from spack.installer import PackageInstaller, InstallError
 from spack.install_test import TestFailure, TestSuite
-from spack.util.executable import which, ProcessError
-from spack.util.prefix import Prefix
-from spack.stage import stage_prefix, Stage, ResourceStage, StageComposite
+from spack.installer import InstallError, PackageInstaller
+from spack.stage import ResourceStage, Stage, StageComposite, stage_prefix
+from spack.util.executable import ProcessError, which
 from spack.util.package_hash import package_hash
+from spack.util.prefix import Prefix
 from spack.version import Version
 
 """Allowed URL schemes for spack packages."""