style: Move isort configuration to pyproject.toml

- [x] Remove flake8-import-order checks, as we only need isort for this
- [x] Clean up configuration and requirements

.flake8

@@ -66,10 +66,6 @@ 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 flake8-import-order isort mypy>=0.800 black types-six types-python-dateutil
+        pip install --upgrade pip six setuptools flake8 isort>=4.3.5 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 flake8-import-order isort pep8-naming mypy
+          pip install --upgrade flake8 isort>=4.3.5 pep8-naming mypy>=0.800
           pip install --upgrade python-dateutil
     - name: Setup Homebrew packages
       run: |

.isort.cfg

@@ -1,11 +0,0 @@
-[settings]
-profile=black
-sections=FUTURE,STDLIB,THIRDPARTY,ARCHSPEC,LLNL,FIRSTPARTY,LOCALFOLDER
-src_paths=lib
-force_sort_within_sections=True
-line_length=79
-known_first_party=spack
-known_archspec=archspec
-known_llnl=llnl
-honor_noqa=True
-use_parentheses=True

lib/spack/spack/cmd/style.py

@@ -219,10 +219,6 @@ def run_flake8(file_list, args):
     print_tool_header("flake8")
     flake8_cmd = which("flake8", required=True)
 
-    # Check if plugins are installed
-    if "import-order" not in flake8_cmd("--version", output=str, error=str):
-        tty.warn("style: flake8-import-order plugin is not installed, skipping")
-
     output = ""
     # run in chunks of 100 at a time to avoid line length limit
     # filename parameter in config *does not work* for this reliably

pyproject.toml

@@ -0,0 +1,14 @@
+[tool.isort]
+profile = "black"
+sections = [
+  "FUTURE",
+  "STDLIB",
+  "THIRDPARTY",
+  "ARCHSPEC", "LLNL", "FIRSTPARTY",
+  "LOCALFOLDER",
+]
+known_first_party = "spack"
+known_archspec = "archspec"
+known_llnl = "llnl"
+src_paths = "lib"
+honor_noqa = true