scripts: print usage in argparse-using scripts when a command-line error occurs

For scripts that use Python's standard argparse module to parse
command-line arguments, create a subclass which will show the usage
the usage information when a command-line parsing error occurs. The most
common case would be when the script is run with no arguments; at least
then the user immediately gets to see what arguments they might need to
pass instead of just an error message.

(From OE-Core rev: d62fe7c9bc2df6a4464440a3cae0539074bf99aa)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/oe-selftest

@@ -36,6 +36,7 @@ sys.path.insert(0, os.path.dirname(os.path.realpath(__file__)) + '/lib')
 import scriptpath
 scriptpath.add_bitbake_lib_path()
 scriptpath.add_oe_lib_path()
+import argparse_oe
 
 import oeqa.selftest
 import oeqa.utils.ftools as ftools
@@ -65,7 +66,7 @@ log = logger_create()
 
 def get_args_parser():
     description = "Script that runs unit tests agains bitbake and other Yocto related tools. The goal is to validate tools functionality and metadata integrity. Refer to https://wiki.yoctoproject.org/wiki/Oe-selftest for more information."
-    parser = argparse.ArgumentParser(description=description)
+    parser = argparse_oe.ArgumentParser(description=description)
     group = parser.add_mutually_exclusive_group(required=True)
     group.add_argument('--run-tests', required=False, action='store', nargs='*', dest="run_tests", default=None, help='Select what tests to run (modules, classes or test methods). Format should be: <module>.<class>.<test_method>')
     group.add_argument('--run-all-tests', required=False, action="store_true", dest="run_all_tests", default=False, help='Run all (unhidden) tests')