treewide: Use argparse.FileType in more places

Convert some scripts to use `argparse.FileType` where the change is relatively
easily doable. This allows better error messages as e.g. missing input files
will be detected during argument parsing. And it also makes writing to stdout
in absence of an explicit argument simpler.

Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Documentation/gen-doxyfile.py

@@ -12,15 +12,6 @@ import string
 import sys
 
 
-def fill_template(template, data):
-
-    template = open(template, 'rb').read()
-    template = template.decode('utf-8')
-    template = string.Template(template)
-
-    return template.substitute(data)
-
-
 def main(argv):
 
     parser = argparse.ArgumentParser()
@@ -28,7 +19,8 @@ def main(argv):
                         type=argparse.FileType('w', encoding='utf-8'),
                         default=sys.stdout,
                         help='Output file name (default: standard output)')
-    parser.add_argument('template', metavar='doxyfile.tmpl', type=str,
+    parser.add_argument('template', metavar='doxyfile.tmpl',
+                        type=argparse.FileType('r', encoding='utf-8'),
                         help='Doxyfile template')
     parser.add_argument('inputs', type=str, nargs='*',
                         help='Input files')
@@ -36,7 +28,9 @@ def main(argv):
     args = parser.parse_args(argv[1:])
 
     inputs = [f'"{os.path.realpath(input)}"' for input in args.inputs]
-    data = fill_template(args.template, {'inputs': (' \\\n' + ' ' * 25).join(inputs)})
+    data = string.Template(args.template.read()).substitute({
+        'inputs': (' \\\n' + ' ' * 25).join(inputs),
+    })
     args.output.write(data)
 
     return 0