precommit: Add check for Python shebang

src/start/python/sample_force_env.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #  vim: set ts=4 sw=4 tw=0 :
 
 from tempfile import NamedTemporaryFile

src/start/python/setup.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #  vim: set ts=4 sw=4 tw=0 :
 
 from distutils.core import setup

src/start/python/test/test_force_env.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #  vim: set ts=4 sw=4 tw=0 :
 
 import unittest

src/start/python/test/test_standalone.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 import unittest
 from tempfile import NamedTemporaryFile

tools/precommit/check_file_properties.py

@@ -3,6 +3,7 @@
 # author: Ole Schuett & Tiziano Müller
 
 import argparse
+import os
 import pathlib
 import re
 import sys
@@ -125,6 +126,7 @@ def check_file(path: pathlib.Path) -> typing.List[str]:
     fn_ext = path.suffix
     abspath = path.resolve()
     basefn = path.name
+    is_executable = os.access(abspath, os.X_OK)
 
     if not PORTABLE_FILENAME_RE.match(str(path)):
         warnings += [f"Filename '{path}' not portable"]
@@ -155,6 +157,11 @@ def check_file(path: pathlib.Path) -> typing.List[str]:
     if fn_ext in C_EXTENSIONS and not content.startswith(BANNER_C.format(year, spdx)):
         warnings += [f"{path}: Copyright banner malformed"]
 
+    # check shebang
+    PY_SHEBANG = "#!/usr/bin/env python3"
+    if fn_ext == ".py" and is_executable and not content.startswith(f"{PY_SHEBANG}\n"):
+        warnings += [f"{path}: Wrong shebang, please use '{PY_SHEBANG}'"]
+
     # find all flags
     flags = set()
     line_continuation = False