enable code linting check for all supported Python versions

.github/workflows/linting.yml

@@ -3,13 +3,17 @@ on: [push, pull_request]
 jobs:
   python-linting:
     runs-on: ubuntu-18.04
+    strategy:
+      matrix:
+        python-version: [2.7, 3.5, 3.6, 3.7, 3.8, 3.9, '3.10']
+
     steps:
     - uses: actions/checkout@v2
 
     - name: set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: 3.8
+        python-version: ${{ matrix.python-version }}
 
     - name: install Python packages
       run: |
@@ -18,4 +22,10 @@ jobs:
 
     - name: Run flake8 to verify PEP8-compliance of Python code
       run: |
-        flake8
+        # don't check py2vs3/py3.py when testing with Python 2, and vice versa
+        if [[ "${{ matrix.python-version }}" =~ "2." ]]; then
+            py_excl=py3
+        else
+            py_excl=py2
+        fi
+        flake8 --exclude ./easybuild/tools/py2vs3/${py_excl}.py

easybuild/framework/easyblock.py

@@ -1485,12 +1485,11 @@ def make_module_req(self):
                 if key in keys_requiring_files:
                     # only retain paths that contain at least one file
                     recursive = keys_requiring_files[key]
-                    retained_paths = [
-                        path
-                        for path, fullpath in ((path, os.path.join(self.installdir, path)) for path in paths)
-                        if os.path.isdir(fullpath)
-                        and dir_contains_files(fullpath, recursive=recursive)
-                    ]
+                    retained_paths = []
+                    for pth in paths:
+                        fullpath = os.path.join(self.installdir, pth)
+                        if os.path.isdir(fullpath) and dir_contains_files(fullpath, recursive=recursive):
+                            retained_paths.append(pth)
                     if retained_paths != paths:
                         self.log.info("Only retaining paths for %s that contain at least one file: %s -> %s",
                                       key, paths, retained_paths)

easybuild/tools/configobj.py

@@ -2023,7 +2023,7 @@ def write(self, outfile=None, section=None):
             # might need to encode
             # NOTE: This will *screw* UTF16, each line will start with the BOM
             if self.encoding:
-                out = [line.encode(self.encoding) for line in out]
+                out = [lne.encode(self.encoding) for lne in out]
             if (self.BOM and ((self.encoding is None) or
                               (BOM_LIST.get(self.encoding.lower()) == 'utf_8'))):
                 # Add the UTF8 BOM