add argparse exception for banner

pwndbg/commands/context.py

@@ -133,12 +133,14 @@ parser.description = "Sets the output of a context section."
 parser.add_argument("section", type=str, help="The section which is to be configured. ('regs', 'disasm', 'code', 'stack', 'backtrace', and/or 'args')")
 parser.add_argument("path", type=str, help="The path to which the output is written")
 parser.add_argument("clearing", type=bool, help="Indicates weather to clear the output")
-parser.add_argument("banner", type=str, nargs='?', default="both", help="Where a banner should be placed: both, top , bottom, none")
+banner_arg = parser.add_argument("banner", type=str, nargs='?', default="both", help="Where a banner should be placed: both, top , bottom, none")
 parser.add_argument("width", type=int, nargs='?', default=None, help="Sets a fixed width (used for banner). Set to None for auto")
 @pwndbg.commands.ArgparsedCommand(parser, aliases=['ctx-out'])
 def contextoutput(section, path, clearing, banner="both", width=None):
+    if banner not in ('both', 'top', 'bottom', 'none'):
+        raise argparse.ArgumentError(banner_arg, f"banner can not be '{banner}'")
     if width is not None:
-        width = int(width.cast(gdb.lookup_type('long')))
+        width = int(width)
     outputs[section] = path
     output_settings[section] = dict(clearing=clearing,
                                     width=width,