id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
26952	Mention the need to install libffi-dev prior to installing packages for tests	Ed Morley	Damian	"The contributing guide explains how to install the Python packages required to run the tests in a couple of places:
https://docs.djangoproject.com/en/dev/intro/contributing/#running-django-s-test-suite-for-the-first-time
https://docs.djangoproject.com/en/dev/internals/contributing/writing-code/unit-tests/#running-all-the-tests

However the `pip install tests/requirements/py*.txt` will fail during the installation of `argon2-cffi` unless `libffi-dev` is installed, with a delightful error like:

{{{
$ pip install -r requirements/py2.txt
Collecting argon2-cffi>=16.1.0 (from -r requirements/base.txt (line 1))
  Downloading argon2_cffi-16.1.0.tar.gz (1.2MB)
    100% |################################| 1.2MB 1.1MB/s
    Complete output from command python setup.py egg_info:
    c/_cffi_backend.c:15:17: fatal error: ffi.h: No such file or directory
    compilation terminated.
    Traceback (most recent call last):
      File ""<string>"", line 1, in <module>
      File ""/tmp/pip-build-PCA0QU/argon2-cffi/setup.py"", line 160, in <module>
        extras_require=EXTRAS_REQUIRE,
      File ""/usr/lib/python2.7/distutils/core.py"", line 111, in setup
        _setup_distribution = dist = klass(attrs)
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/setuptools/dist.py"", line 348, in __init__
        self.fetch_build_eggs(attrs['setup_requires'])
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/setuptools/dist.py"", line 394, in fetch_build_eggs
        replace_conflicting=True,
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/pkg_resources/__init__.py"", line 826, in resolve
        dist = best[req.key] = env.best_match(req, ws, installer)
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/pkg_resources/__init__.py"", line 1092, in best_match
        return self.obtain(req, installer)
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/pkg_resources/__init__.py"", line 1104, in obtain
        return installer(requirement)
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/setuptools/dist.py"", line 461, in fetch_build_egg
        return cmd.easy_install(req)
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/setuptools/command/easy_install.py"", line 664, in easy_install
        return self.install_item(spec, dist.location, tmpdir, deps)
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/setuptools/command/easy_install.py"", line 694, in install_item
        dists = self.install_eggs(spec, download, tmpdir)
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/setuptools/command/easy_install.py"", line 875, in install_eggs
        return self.build_and_install(setup_script, setup_base)
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/setuptools/command/easy_install.py"", line 1114, in build_and_install
        self.run_setup(setup_script, setup_base, args)
      File ""/home/vagrant/.virtualenvs/django/local/lib/python2.7/site-packages/setuptools/command/easy_install.py"", line 1102, in run_setup
        raise DistutilsError(""Setup script exited with %s"" % (v.args[0],))
    distutils.errors.DistutilsError: Setup script exited with error: command 'x86_64-linux-gnu-gcc' failed with exit status 1

    ----------------------------------------
Command ""python setup.py egg_info"" failed with error code 1 in /tmp/pip-build-PCA0QU/argon2-cffi/
}}}


Many people will know immediately what the issue is (or one would hope after Googling), however it would probably be good to state the requirement explicitly  and also mention in the troubleshooting section :-)"	Cleanup/optimization	closed	Documentation	dev	Normal	fixed			Accepted	0	0	0	0	1	0