Minor cleanup ValidateOptions doc/code/test

Some nearby things in Main.py as well:
- docstrings polished a bit, minor linting
- move the list of predefined SConstruct file names into a constant
  defined at the top of the file, so it's a little less hidden,
  in the unlikely case of future changes.

Manpage text and example revised a bit.

Signed-off-by: Mats Wichmann <mats@linux.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/test/fixture/SConstruct-check-valid-options b/test/fixture/SConstruct-check-valid-options
index 2c935a23c..53bdf89d3 100644
--- a/test/fixture/SConstruct-check-valid-options
+++ b/test/fixture/SConstruct-check-valid-options
@@ -1,3 +1,7 @@
+# SPDX-License-Identifier: MIT
+#
+# Copyright The SCons Foundation
+
 import sys
 from SCons.Script.SConsOptions import SConsOptionParser, SConsBadOptionError
 
@@ -12,8 +16,10 @@ elif ARGUMENTS.get('raise', 0) == '2':
     try:
         ValidateOptions(throw_exception=True)
     except SConsBadOptionError as e:
-        print("Parser is SConsOptionParser:%s" % (isinstance(e.parser, SConsOptionParser)))
-        print("Message is :%s" % e.opt_str)
+        print(
+            f"Parser is SConsOptionParser: {isinstance(e.parser, SConsOptionParser)}"
+        )
+        print(f"Message is: {e.opt_str}")
         Exit(3)
 else:
     ValidateOptions()