dephell doesn't pin virtualenv deps

[graingert]

Short description

Output

actual:

virtualenv
virtualenv==20.0.31 \
  --hash sha256:43add625c53c596d38f971a465553f6318decc39d98512bc100fa1b1e839c8dc \
  --hash sha256:e0305af10299a7fb0d69393d8f04cb2965dda9351140d11ac8db4e5e3970451b \
  # ^ from root

I expect distlib and filelock etc in there

Steps to reproduce

https://asciinema.org/a/z7y3VDOabSaFukIge79tyWmHw?t=50

echo "virtualenv" > requirements.in
pipx run dephell -- convert --from=requirements.in --to=requirements.lock
python3.8 -m venv .venv
.venv/bin/python -m pip install -crequirements.lock virtualenv

Config

no config

Versions

WARNING cannot find config file 
WARNING cannot find module, trying to install (package=pygments)
Collecting pygments
Installing collected packages: pygments
Successfully installed pygments-2.7.0

{
  "cache": "22.34Mb",
  "path": "/home/graingert/.local/pipx/.cache/8c391109890bc16/lib/python3.8/site-packages/dephell",
  "python": "/home/graingert/.local/pipx/.cache/8c391109890bc16/bin/python",
  "version": "0.8.3",
  "versions": {
    "dephell-archive": "0.1.7",
    "dephell-argparse": "0.1.3",
    "dephell-changelogs": "0.0.1",
    "dephell-discover": "0.2.10",
    "dephell-licenses": "0.1.7",
    "dephell-links": "0.1.5",
    "dephell-markers": "1.0.3",
    "dephell-pythons": "0.1.15",
    "dephell-setuptools": "0.2.4",
    "dephell-shells": "0.1.5",
    "dephell-specifier": "0.2.2",
    "dephell-venvs": "0.1.17",
    "dephell-versioning": "0.1.2"
  }
}

[graingert]

@orsinium