Virtualenv not completely deleted after package removal

[emkll]

Initially reported by @kushaldas in freedomofpress/securedrop-workstation#447 (comment)

Some files are preserved in the virtualenv after uninstalling packages. After running sudo apt remove securedrop-*, the following files remain in /opt/virtualenvs/:

While the sd-log remaining files is likely due to a bytecode parameter, other packages still have python3,orig.

sd-log

/opt/venvs/
└── securedrop-log
    ├── bin
    │   └── python3,orig
    └── lib
        └── python3.7
            └── __pycache__
                ├── abc.cpython-37.pyc
                ├── _bootlocale.cpython-37.pyc
                ├── codecs.cpython-37.pyc
                ├── _collections_abc.cpython-37.pyc
                ├── copyreg.cpython-37.pyc
                ├── enum.cpython-37.pyc
                ├── functools.cpython-37.pyc
                ├── genericpath.cpython-37.pyc
                ├── heapq.cpython-37.pyc
                ├── io.cpython-37.pyc
                ├── keyword.cpython-37.pyc
                ├── linecache.cpython-37.pyc
                ├── operator.cpython-37.pyc
                ├── os.cpython-37.pyc
                ├── posixpath.cpython-37.pyc
                ├── re.cpython-37.pyc
                ├── reprlib.cpython-37.pyc
                ├── site.cpython-37.pyc
                ├── sre_compile.cpython-37.pyc
                ├── sre_constants.cpython-37.pyc
                ├── sre_parse.cpython-37.pyc
                ├── stat.cpython-37.pyc
                ├── token.cpython-37.pyc
                ├── tokenize.cpython-37.pyc
                ├── types.cpython-37.pyc
                ├── warnings.cpython-37.pyc
                ├── weakref.cpython-37.pyc
                └── _weakrefset.cpython-37.pyc

5 directories, 29 files

sd-app

/opt/venvs/
└── securedrop-client
    └── bin
        └── python3,orig

2 directories, 1 file

sd-proxy

/opt/venvs/
└── securedrop-proxy
    └── bin
        └── python3,orig

2 directories, 1 file

sd-devices

/opt/venvs/
└── securedrop-export
    └── bin
        └── python3,orig

2 directories, 1 file