Cannot create requirement from this particular pip freeze output

Nobody has claimed this yet.

If you install a package in a subdirectory from git, e.g.

```
git+ssh://git@github.com/my/repo.git@project25#egg=PACKAGE_NAME&subdirectory=SUB_DIR/
```

and then do a `pip freeze` you'll instead get:

```
PACKAGE_NAME @ git+ssh://git@github.com/my/repo.git@3684f02bf928cae39d10d1d9b478d95d2267b2af#subdirectory=SUB_DIR/
```

In which case this cannot be parsed (redacted with parts I can't share):

```
File "/stitchfix/z-pyenv/pyenv/versions/3.6/lib/python3.6/site-packages/requirements/parser.py", line 50, in parse yield Requirement.parse(line)
File "/stitchfix/z-pyenv/pyenv/versions/3.6/lib/python3.6/site-packages/requirements/requirement.py", line 220, in parse return cls.parse_line(line)
File "/stitchfix/z-pyenv/pyenv/versions/3.6/lib/python3.6/site-packages/requirements/requirement.py", line 198, in parse_line pkg_req = Req.parse(line)
File "/stitchfix/z-pyenv/pyenv/versions/3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3155, in parse req, = parse_requirements(s)

Traceback (most recent call last):
File "/stitchfix/z-pyenv/pyenv/versions/3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3108, in __init__ super(Requirement, self).__init__(requirement_string)
File "/stitchfix/z-pyenv/pyenv/versions/3.6/lib/python3.6/site-packages/pkg_resources/_vendor/packaging/requirements.py", line 101, in __init__ raise InvalidRequirement("Invalid URL given")
pkg_resources.extern.packaging.requirements.InvalidRequirement: Invalid URL given
```

Start by reproducing the failure with the pip freeze line shown in the issue, then inspect requirements/parser.py and requirements/requirement.py around the reported parsing calls. Done means the git URL with the package name and subdirectory is accepted and parsed without the Invalid URL given error.

Written by the indexing model from the issue text.