scripts: add spdxcheck.py self test

Add a script that will run spdxcheck.py through a couple of self tests to
simplify validation in the future. The tests are run for both Python 2
and Python 3 to make sure all changes to the script remain compatible
across both versions.

The script tests a regular text file (Makefile) for basic sanity checks
and then runs it on a binary file (Documentation/logo.gif) to make sure it
works in both cases. It also tests opening files passed on the command
line as well as piped files read from standard input. Finally a run on
the complete tree will be performed to catch any other potential issues.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Thierry Reding <[e-mail]>
Thomas Gleixner <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Joe Perches <[e-mail]>
Cc: Jeremy Cline <[e-mail]>
Cc: Uwe Kleine-König <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

scripts/spdxcheck-test.sh

···
+#!/bin/sh
+
+for PYTHON in python2 python3; do
+	# run check on a text and a binary file
+	for FILE in Makefile Documentation/logo.gif; do
+		$PYTHON scripts/spdxcheck.py $FILE
+		$PYTHON scripts/spdxcheck.py - < $FILE
+	done
+
+	# run check on complete tree to catch any other issues
+	$PYTHON scripts/spdxcheck.py > /dev/null
+done