Handle case when executable is not executable

- Changed error message if executable is not executable

Closes:[1159](https://github.com/pre-commit/pre-commit/issues/1159)

pre_commit/parse_shebang.py

@@ -51,10 +51,12 @@ def normexe(orig):
         if exe is None:
             _error('not found')
         return exe
-    elif not os.access(orig, os.X_OK):
-        _error('not found')
     elif os.path.isdir(orig):
         _error('is a directory')
+    elif not os.path.isfile(orig):
+        _error('not found')
+    elif not os.access(orig, os.X_OK):  # pragma: windows no cover
+        _error('is not executable')
     else:
         return orig
 

tests/parse_shebang_test.py

@@ -91,6 +91,14 @@ def test_normexe_does_not_exist_sep():
     assert excinfo.value.args == ('Executable `./i-dont-exist-lol` not found',)
 
 
+@pytest.mark.xfail(os.name == 'nt', reason='posix only',)
+def test_normexe_not_executable(tmpdir):  # pragma: windows no cover
+    tmpdir.join('exe').ensure()
+    with tmpdir.as_cwd(), pytest.raises(OSError) as excinfo:
+        parse_shebang.normexe('./exe')
+    assert excinfo.value.args == ('Executable `./exe` is not executable',)
+
+
 def test_normexe_is_a_directory(tmpdir):
     with tmpdir.as_cwd():
         tmpdir.join('exe').ensure_dir()