[PATCH] checkpatch: Follow scripts/spdxcheck.py's switch to python3

[Vincent Pelletier <plr.vincent@gmail.com>]

Since commit d0259c42abff ("spdxcheck.py: Use Python 3") spdxcheck.py
expects to be run using python3. "python" may still be a python2 alias.
Instead, obey scripts/spdxcheck.py's shebang by executing it without
pre-selecting an interpreter.
Also, test python3 presence in path.

Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com>
---
 scripts/checkpatch.pl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 23697a6b1eaa..a1cbd5fd0856 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -1084,10 +1084,10 @@ sub is_maintained_obsolete {
 sub is_SPDX_License_valid {
 	my ($license) = @_;
 
-	return 1 if (!$tree || which("python") eq "" || !(-e "$root/scripts/spdxcheck.py") || !(-e "$gitroot"));
+	return 1 if (!$tree || which("python3") eq "" || !(-e "$root/scripts/spdxcheck.py") || !(-e "$gitroot"));
 
 	my $root_path = abs_path($root);
-	my $status = `cd "$root_path"; echo "$license" | python scripts/spdxcheck.py -`;
+	my $status = `cd "$root_path"; echo "$license" | scripts/spdxcheck.py -`;
 	return 0 if ($status ne "");
 	return 1;
 }
-- 
2.32.0