Fails to parse requirement with trailing whitespace

[gaborbernat]

from packaging.requirements import Requirement

req = "pycontracts @ https://github.com/slorg1/contracts/archive/c5a6da27d4dc9985f68e574d20d86000880919c3.zip "
Requirement(req)

packaging._tokenizer.ParserSyntaxError: Expected end or semicolon (after URL and whitespace)
    pycontracts @ https://github.com/slorg1/contracts/archive/c5a6da27d4dc9985f68e574d20d86000880919c3.zip 
                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/bgabor8/git/github/tox/magic.py", line 4, in <module>
    Requirement(req)
  File "/Users/bgabor8/git/github/tox/.tox/dev/lib/python3.11/site-packages/packaging/requirements.py", line 37, in __init__
    raise InvalidRequirement(str(e)) from e
packaging.requirements.InvalidRequirement: Expected end or semicolon (after URL and whitespace)
    pycontracts @ https://github.com/slorg1/contracts/archive/c5a6da27d4dc9985f68e574d20d86000880919c3.zip 
                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^

Would you happen to know if this is expected? If you remove the trailing whitespace, the parsing succeeds. Parsing attrs works, so this is slightly unexpected. Initially reported via tox-dev/tox#2773

[pradyunsg]

Covered by #642.