I've attached a patch making the changes I suggested, assuming that the current behaviour is desirable. It documents the behaviour of argparse on files with blank lines and changes the way the error message that argparse generates when encountering unrecognized arguments is generated.

When a blank line is included at the end of a file, the resulting error message is now: "argparse_example.py: error: unrecognized arguments: ''". This also makes it obvious when the problem is white space, e.g. if an argument has trailing spaces, this also makes that obvious.