title: How to tell Pipenv ignore a package in Pipfile based on the OS
body: <p>I am creating a Python project using Pipenv and I have the following Pipfile:</p>
  
  <pre><code>[[source]]
  name = "pypi"
  url = "https://pypi.org/simple"
  verify_ssl = true
  
  [dev-packages]
  black = "==19.10b0"
  pylint = "==2.4.4"
  pytest = "==5.3.1"
  pytest-mock = "==1.13.0"
  pytest-flask = "==0.15.0"
  
  [packages]
  python-decouple = "==3.3"
  pytz = "*"
  Flask = "==1.1.1"
  Flask-RESTful = "==0.3.7"
  uWSGI = "==2.0.18"
  
  [requires]
  python_version = "3.8"
  </code></pre>
  
  <p>My problem is that the <code>uWSGI</code> package is only available for Linux and I am using Windows. So whenever I run <code>pipenv install</code> it fails because of it. Is there a way to tell Pipenv to ignore the installation of this package only on a Windows environment?</p>
  
  <p><strong>UPDATE</strong></p>
  
  <p>Here is the result of the command: <code>pipenv lock -r</code></p>
  
  <pre><code>Pipfile.lock (e1b4e4) out of date, updating to (5696f6)…
  Locking [dev-packages] dependencies…
  Success!
  Locking [packages] dependencies…
  Locking Failed!
  Traceback (most recent call last):
    File "c:/users/felipe a/appdata/local/programs/python/python38-32/lib/site-packages/pipenv/resolver.py", line 126, in &lt;module&gt;
      main()
    File "c:/users/felipe a/appdata/local/programs/python/python38-32/lib/site-packages/pipenv/resolver.py", line 118, in main
      _main(parsed.pre, parsed.clear, parsed.verbose, parsed.system,
    File "c:/users/felipe a/appdata/local/programs/python/python38-32/lib/site-packages/pipenv/resolver.py", line 78, in _main
      results = resolve(
    File "c:/users/felipe a/appdata/local/programs/python/python38-32/lib/site-packages/pipenv/resolver.py", line 61, in resolve
      return resolve_deps(
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\utils.py", line 718, in resolve_deps
      resolved_tree, hashes, markers_lookup, resolver = actually_resolve_deps(
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\utils.py", line 480, in actually_resolve_deps
      resolved_tree = resolver.resolve()
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\utils.py", line 385, in resolve
      results = self.resolver.resolve(max_rounds=environments.PIPENV_MAX_ROUNDS)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\resolver.py", line 102, in resolve
      has_changed, best_matches = self._resolve_one_round()
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\resolver.py", line 206, in _resolve_one_round
      for dep in self._iter_dependencies(best_match):
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\resolver.py", line 301, in _iter_dependencies
      dependencies = self.repository.get_dependencies(ireq)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\repositories\pypi.py", line 234, in get_dependencies
      legacy_results = self.get_legacy_dependencies(ireq)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\repositories\pypi.py", line 426, in get_legacy_dependencies
      results, ireq = self.resolve_reqs(download_dir, ireq, wheel_cache)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\repositories\pypi.py", line 297, in resolve_reqs
      results = resolver._resolve_one(reqset, ireq)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\resolve.py", line 260, in _resolve_one
      abstract_dist = self._get_abstract_dist_for(req_to_install)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\resolve.py", line 211, in _get_abstract_dist_for
      abstract_dist = self.preparer.prepare_linked_requirement(
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\operations\prepare.py", line 294, in prepare_linked_requirement
      abstract_dist.prep_for_dist(finder, self.build_isolation)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\operations\prepare.py", line 127, in prep_for_dist
      self.req.run_egg_info()
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\req\req_install.py", line 470, in run_egg_info
      call_subprocess(
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\utils\misc.py", line 703, in call_subprocess
      raise InstallationError(
  pipenv.patched.notpip._internal.exceptions.InstallationError: Command "python setup.py egg_info" failed with error code 1 in C:\Users\FELIPE~1\AppData\Local\Temp\tmpuyfdyzgwbuild\uwsgi\
  File "c:/users/felipe a/appdata/local/programs/python/python38-32/lib/site-packages/pipenv/resolver.py", line 126, in &lt;module&gt;
      main()
    File "c:/users/felipe a/appdata/local/programs/python/python38-32/lib/site-packages/pipenv/resolver.py", line 118, in main
      _main(parsed.pre, parsed.clear, parsed.verbose, parsed.system,
    File "c:/users/felipe a/appdata/local/programs/python/python38-32/lib/site-packages/pipenv/resolver.py", line 78, in _main
      results = resolve(
    File "c:/users/felipe a/appdata/local/programs/python/python38-32/lib/site-packages/pipenv/resolver.py", line 61, in resolve
      return resolve_deps(
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\utils.py", line 718, in resolve_deps
      resolved_tree, hashes, markers_lookup, resolver = actually_resolve_deps(
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\utils.py", line 480, in actually_resolve_deps
      resolved_tree = resolver.resolve()
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\utils.py", line 385, in resolve
      results = self.resolver.resolve(max_rounds=environments.PIPENV_MAX_ROUNDS)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\resolver.py", line 102, in resolve
      has_changed, best_matches = self._resolve_one_round()
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\resolver.py", line 206, in _resolve_one_round
      for dep in self._iter_dependencies(best_match):
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\resolver.py", line 301, in _iter_dependencies
      dependencies = self.repository.get_dependencies(ireq)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\repositories\pypi.py", line 234, in get_dependencies
      legacy_results = self.get_legacy_dependencies(ireq)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\repositories\pypi.py", line 426, in get_legacy_dependencies
      results, ireq = self.resolve_reqs(download_dir, ireq, wheel_cache)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\piptools\repositories\pypi.py", line 297, in resolve_reqs
      results = resolver._resolve_one(reqset, ireq)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\resolve.py", line 260, in _resolve_one
      abstract_dist = self._get_abstract_dist_for(req_to_install)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\resolve.py", line 211, in _get_abstract_dist_for
      abstract_dist = self.preparer.prepare_linked_requirement(
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\operations\prepare.py", line 294, in prepare_linked_requirement
      abstract_dist.prep_for_dist(finder, self.build_isolation)
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\operations\prepare.py", line 127, in prep_for_dist
      self.req.run_egg_info()
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\req\req_install.py", line 470, in run_egg_info
      call_subprocess(
    File "c:\users\felipe a\appdata\local\programs\python\python38-32\lib\site-packages\pipenv\patched\notpip\_internal\utils\misc.py", line 703, in call_subprocess
      raise InstallationError(
  pipenv.patched.notpip._internal.exceptions.InstallationError: Command "python setup.py egg_info" failed with error code 1 in C:\Users\FELIPE~1\AppData\Local\Temp\tmpuyfdyzgwbuild\uwsgi\
  </code></pre>