pipenv ignore environment variable `PIP_TARGET` when calculate dependancy delta.

[cm-iwata]

Issue description

Sometimes I use pipenv with environment variable PIP_TARGET for install libraries to specified directory.
But pipenv will skip install libraries if libraries already install to default location.

Expected result

pipenv should install libraries to specified directory when exec with environment variable PIP_TARGET.

Actual result

pipenv will skip install libraries to specified directory when libraries already installed to default location(.venv/lib/pythonx.x/site-packages).

Steps to replicate

1. install some library and create Pipfile.lock

pipenv install six

2. Create some directory for specify pip install target.

mkdir layer

3. Try install library to specified directory.

PIP_TARGET=layer  pipenv sync
Installing dependencies from Pipfile.lock (34ad89)…
  🐍   ▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉▉ 0/0 — 0

Install library will skip and output 0/0 — 00:00:00

4. List specified directory.There are no library.

ls layer

This command will return empty result.

$ pipenv --support

Pipenv version: '2020.6.2'

Pipenv location: '/Users/cm-iwata/.anyenv/envs/pyenv/versions/3.8.3/lib/python3.8/site-packages/pipenv'

Python location: '/Users/cm-iwata/.anyenv/envs/pyenv/versions/3.8.3/bin/python3.8'

Python installations found:

• 3.9.2: /usr/local/bin/python3
• 3.9.2: /usr/local/bin/python3.9
• 3.8.3: /Users/cm-iwata/.anyenv/envs/pyenv/versions/3.8.3/bin/python3
• 3.8.3: /Users/cm-iwata/.anyenv/envs/pyenv/versions/3.8.3/bin/python3.8
• 3.8.3: /Users/cm-iwata/.anyenv/envs/pyenv/versions/3.8.3/bin/python3
• 3.7.8: /Users/cm-iwata/.anyenv/envs/pyenv/versions/3.7.8/bin/python3
• 3.7.3: /usr/bin/python3
• 3.6.5: /Users/cm-iwata/.anyenv/envs/pyenv/versions/3.6.5/bin/python3
• 3.6.1: /Users/cm-iwata/.anyenv/envs/pyenv/versions/3.6.1/bin/python3
• 2.7.16: /usr/bin/python2
• 2.7.16: /usr/bin/python2.7

PEP 508 Information:

{'implementation_name': 'cpython',
 'implementation_version': '3.8.3',
 'os_name': 'posix',
 'platform_machine': 'x86_64',
 'platform_python_implementation': 'CPython',
 'platform_release': '19.5.0',
 'platform_system': 'Darwin',
 'platform_version': 'Darwin Kernel Version 19.5.0: Tue May 26 20:41:44 PDT '
                     '2020; root:xnu-6153.121.2~2/RELEASE_X86_64',
 'python_full_version': '3.8.3',
 'python_version': '3.8',
 'sys_platform': 'darwin'}

System environment variables:

• LDFLAGS
• TERM_PROGRAM
• NODENV_SHELL
• PYENV_ROOT
• SHELL
• TERM
• TMPDIR
• CPPFLAGS
• PIPENV_VENV_IN_PROJECT
• TERM_PROGRAM_VERSION
• GOENV_ROOT
• TERM_SESSION_ID
• PYENV_VERSION
• NODENV_ROOT
• LC_ALL
• USER
• RBENV_ROOT
• SSH_AUTH_SOCK
• PYENV_DIR
• __CF_USER_TEXT_ENCODING
• PATH
• LaunchInstanceID
• PWD
• LANG
• ITERM_PROFILE
• CLOUDSDK_PYTHON
• PYENV_HOOK_PATH
• XPC_FLAGS
• RBENV_SHELL
• XPC_SERVICE_NAME
• HISTCONTROL
• COLORFGBG
• HOME
• SHLVL
• PYENV_SHELL
• LC_TERMINAL_VERSION
• ITERM_SESSION_ID
• LOGNAME
• GOENV_SHELL
• LC_TERMINAL
• SECURITYSESSIONID
• COLORTERM
• PIP_DISABLE_PIP_VERSION_CHECK
• PYTHONDONTWRITEBYTECODE
• PIP_SHIMS_BASE_MODULE
• PIP_PYTHON_PATH
• PYTHONFINDER_IGNORE_UNSUPPORTED

Pipenv–specific environment variables:

• PIPENV_VENV_IN_PROJECT: 1

Debug–specific environment variables:

• PATH: /Users/cm-iwata/.anyenv/envs/pyenv/versions/3.8.3/bin:/Users/cm-iwata/.anyenv/envs/pyenv/libexec:/Users/cm-iwata/.anyenv/envs/pyenv/plugins/python-build/bin:/Users/cm-iwata/gcp/google-cloud-sdk/bin:/usr/local/bin:/usr/local/opt/mysql-client/bin:/Users/cm-iwata/.anyenv/envs/rbenv/shims:/Users/cm-iwata/.anyenv/envs/rbenv/bin:/Users/cm-iwata/.anyenv/envs/pyenv/shims:/Users/cm-iwata/.anyenv/envs/pyenv/bin:/Users/cm-iwata/.anyenv/envs/nodenv/shims:/Users/cm-iwata/.anyenv/envs/nodenv/bin:/Users/cm-iwata/.anyenv/envs/goenv/shims:/Users/cm-iwata/.anyenv/envs/goenv/bin:/Users/cm-iwata/.anyenv/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/share/dotnet:~/.dotnet/tools:/Applications/Visual Studio Code.app/Contents/Resources/app/bin
• SHELL: /bin/bash
• LANG: en_US.UTF-8
• PWD: /tmp/pipenvtest2

---

Contents of Pipfile ('/private/tmp/pipenvtest2/Pipfile'):

[[source]]
name = "pypi"
url = "https://pypi.org/simple"
verify_ssl = true

[dev-packages]

[packages]
six = "*"

[requires]
python_version = "3.8"

Contents of Pipfile.lock ('/private/tmp/pipenvtest2/Pipfile.lock'):

{
    "_meta": {
        "hash": {
            "sha256": "d9b5cc506fc4feb9bf1ae7cadfd3737d5a0bd2b2d6c3fbcf0de3458bab34ad89"
        },
        "pipfile-spec": 6,
        "requires": {
            "python_version": "3.8"
        },
        "sources": [
            {
                "name": "pypi",
                "url": "https://pypi.org/simple",
                "verify_ssl": true
            }
        ]
    },
    "default": {
        "six": {
            "hashes": [
                "sha256:1e61c37477a1626458e36f7b1d82aa5c9b094fa4802892072e49de9c60c4c926",
                "sha256:8abb2f1d86890a2dfb989f9a77cfcfd3e47c2a354b01111771326f8aa26e0254"
            ],
            "index": "pypi",
            "version": "==1.16.0"
        }
    },
    "develop": {}
}