I see three solutions - 

1) gholms' patch which removes '() ' and [] '

2) Yogesh's patch which removes all duplicated spaces.

3) remove the 2 asserts. 

The first 2 do the same thing most of the time, but may differ if the user somehow inserts spaces into names.  The third leaves the extra blanks, but renders them innocuous.  I doubt if the asserts were written to catch this problem.  They probably were included to verify the usage line had been split up as expected prior to reassembling on multiple lines.

As best I can tell test_argparse.py does not test for these spaces.  Curiously though a port of argparse to javascript does have a test case with the extra space.