Downloading fails, since build starts

We host a simple pypi server in our company.



This command works for most pip package, but it fails for `argon2-cffi`:



    pypi@pypihost:~> pip install  -d packages argon2-cffi

    Collecting argon2-cffi

      File was already downloaded packages/argon2_cffi-16.2.0.tar.gz

        Complete output from command python setup.py egg_info:

        Package libffi was not found in the pkg-config search path.

        Perhaps you should add the directory containing `libffi.pc'

        to the PKG_CONFIG_PATH environment variable

        No package 'libffi' found

        Package libffi was not found in the pkg-config search path.

        Perhaps you should add the directory containing `libffi.pc'

        to the PKG_CONFIG_PATH environment variable

        No package 'libffi' found

        Package libffi was not found in the pkg-config search path.

        Perhaps you should add the directory containing `libffi.pc'

        to the PKG_CONFIG_PATH environment variable

        No package 'libffi' found

        Package libffi was not found in the pkg-config search path.

        Perhaps you should add the directory containing `libffi.pc'

        to the PKG_CONFIG_PATH environment variable

        No package 'libffi' found

        Package libffi was not found in the pkg-config search path.

        Perhaps you should add the directory containing `libffi.pc'

        to the PKG_CONFIG_PATH environment variable

        No package 'libffi' found

        c/_cffi_backend.c:15:17: fatal error: ffi.h: Datei oder Verzeichnis nicht gefunden

        compilation terminated.

        Traceback (most recent call last):

          File "<string>", line 1, in <module>

          File "/home/pypi/tmp/pip-build-LJ1EjJ/argon2-cffi/setup.py", line 206, in <module>

            extras_require=EXTRAS_REQUIRE,

          File "/usr/lib/python2.7/distutils/core.py", line 112, in setup

            _setup_distribution = dist = klass(attrs)

          File "/home/pypi/lib/python2.7/site-packages/setuptools/dist.py", line 265, in __init__

            self.fetch_build_eggs(attrs['setup_requires'])

          File "/home/pypi/lib/python2.7/site-packages/setuptools/dist.py", line 310, in fetch_build_eggs

            replace_conflicting=True,

          File "/home/pypi/lib/python2.7/site-packages/pkg_resources/__init__.py", line 824, in resolve

            dist = best[req.key] = env.best_match(req, ws, installer)

          File "/home/pypi/lib/python2.7/site-packages/pkg_resources/__init__.py", line 1069, in best_match

            return self.obtain(req, installer)

          File "/home/pypi/lib/python2.7/site-packages/pkg_resources/__init__.py", line 1081, in obtain

            return installer(requirement)

          File "/home/pypi/lib/python2.7/site-packages/setuptools/dist.py", line 377, in fetch_build_egg

            return cmd.easy_install(req)

          File "/home/pypi/lib/python2.7/site-packages/setuptools/command/easy_install.py", line 629, in easy_install

            return self.install_item(spec, dist.location, tmpdir, deps)

          File "/home/pypi/lib/python2.7/site-packages/setuptools/command/easy_install.py", line 659, in install_item

            dists = self.install_eggs(spec, download, tmpdir)

          File "/home/pypi/lib/python2.7/site-packages/setuptools/command/easy_install.py", line 842, in install_eggs

            return self.build_and_install(setup_script, setup_base)

          File "/home/pypi/lib/python2.7/site-packages/setuptools/command/easy_install.py", line 1070, in build_and_install

            self.run_setup(setup_script, setup_base, args)

          File "/home/pypi/lib/python2.7/site-packages/setuptools/command/easy_install.py", line 1058, in run_setup

            raise DistutilsError("Setup script exited with %s" % (v.args[0],))

        distutils.errors.DistutilsError: Setup script exited with error: command 'gcc' failed with exit status 1

        

        ----------------------------------------

    Command "python setup.py egg_info" failed with error code 1 in /home/pypi/tmp/pip-build-LJ1EjJ/argon2-cffi/



I don't want gcc to run in this case, since I only want to **download** it.



What I am doing wrong?



Same issue on StackO: http://stackoverflow.com/questions/40038861/downloading-but-not-installing-argon2-cffi

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