Collecting argon2-cffi>=16.1.0; extra == "argon2" (from django[argon2])
 Downloading argon2_cffi-16.1.0.tar.gz (1.2MB)
   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: No such file or directory
   compilation terminated.
   Traceback (most recent call last):
     File "/usr/lib/python3.5/distutils/unixccompiler.py", line 118, in _compile
       extra_postargs)
     File "/usr/lib/python3.5/distutils/ccompiler.py", line 909, in spawn
       spawn(cmd, dry_run=self.dry_run)
     File "/usr/lib/python3.5/distutils/spawn.py", line 36, in spawn
       _spawn_posix(cmd, search_path, dry_run=dry_run)
     File "/usr/lib/python3.5/distutils/spawn.py", line 159, in _spawn_posix
       % (cmd, exit_status))
   distutils.errors.DistutilsExecError: command 'x86_64-linux-gnu-gcc' failed with exit status 1
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   During handling of the above exception, another exception occurred:
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   Traceback (most recent call last):
     File "/usr/lib/python3.5/distutils/core.py", line 148, in setup
       dist.run_commands()
     File "/usr/lib/python3.5/distutils/dist.py", line 955, in run_commands
       self.run_command(cmd)
     File "/usr/lib/python3.5/distutils/dist.py", line 974, in run_command
       cmd_obj.run()
     File "/usr/lib/python3/dist-packages/setuptools/command/bdist_egg.py", line 161, in run
       cmd = self.call_command('install_lib', warn_dir=0)
     File "/usr/lib/python3/dist-packages/setuptools/command/bdist_egg.py", line 147, in call_command
       self.run_command(cmdname)
     File "/usr/lib/python3.5/distutils/cmd.py", line 313, in run_command
       self.distribution.run_command(command)
     File "/usr/lib/python3.5/distutils/dist.py", line 974, in run_command
       cmd_obj.run()
     File "/usr/lib/python3/dist-packages/setuptools/command/install_lib.py", line 23, in run
       self.build()
     File "/usr/lib/python3.5/distutils/command/install_lib.py", line 109, in build
       self.run_command('build_ext')
     File "/usr/lib/python3.5/distutils/cmd.py", line 313, in run_command
       self.distribution.run_command(command)
     File "/usr/lib/python3.5/distutils/dist.py", line 974, in run_command
       cmd_obj.run()
     File "/usr/lib/python3/dist-packages/setuptools/command/build_ext.py", line 49, in run
       _build_ext.run(self)
     File "/usr/lib/python3.5/distutils/command/build_ext.py", line 338, in run
       self.build_extensions()
     File "/usr/lib/python3.5/distutils/command/build_ext.py", line 447, in build_extensions
       self._build_extensions_serial()
     File "/usr/lib/python3.5/distutils/command/build_ext.py", line 472, in _build_extensions_serial
       self.build_extension(ext)
     File "/usr/lib/python3/dist-packages/setuptools/command/build_ext.py", line 174, in build_extension
       _build_ext.build_extension(self, ext)
     File "/usr/lib/python3.5/distutils/command/build_ext.py", line 532, in build_extension
       depends=ext.depends)
     File "/usr/lib/python3.5/distutils/ccompiler.py", line 574, in compile
       self._compile(obj, src, ext, cc_args, extra_postargs, pp_opts)
     File "/usr/lib/python3.5/distutils/unixccompiler.py", line 120, in _compile
       raise CompileError(msg)
   distutils.errors.CompileError: command 'x86_64-linux-gnu-gcc' failed with exit status 1
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   During handling of the above exception, another exception occurred:
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   Traceback (most recent call last):
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 154, in save_modules
       yield saved
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 195, in setup_context
       yield
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 243, in run_setup
       DirectorySandbox(setup_dir).run(runner)
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 273, in run
       return func()
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 242, in runner
       _execfile(setup_script, ns)
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 46, in _execfile
       exec(code, globals, locals)
     File "/tmp/easy_install-epo8th_s/cffi-1.7.0/setup.py", line 192, in <module>
     File "/usr/lib/python3.5/distutils/core.py", line 163, in setup
       raise SystemExit("error: " + str(msg))
   SystemExit: error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
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   During handling of the above exception, another exception occurred:
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   Traceback (most recent call last):
     File "/usr/lib/python3/dist-packages/setuptools/command/easy_install.py", line 1087, in run_setup
       run_setup(setup_script, args)
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 246, in run_setup
       raise
     File "/usr/lib/python3.5/contextlib.py", line 77, in __exit__
       self.gen.throw(type, value, traceback)
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 195, in setup_context
       yield
     File "/usr/lib/python3.5/contextlib.py", line 77, in __exit__
       self.gen.throw(type, value, traceback)
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 166, in save_modules
       saved_exc.resume()
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 141, in resume
       six.reraise(type, exc, self._tb)
     File "/usr/lib/python3/dist-packages/pkg_resources/_vendor/six.py", line 685, in reraise
       raise value.with_traceback(tb)
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 154, in save_modules
       yield saved
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 195, in setup_context
       yield
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 243, in run_setup
       DirectorySandbox(setup_dir).run(runner)
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 273, in run
       return func()
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 242, in runner
       _execfile(setup_script, ns)
     File "/usr/lib/python3/dist-packages/setuptools/sandbox.py", line 46, in _execfile
       exec(code, globals, locals)
     File "/tmp/easy_install-epo8th_s/cffi-1.7.0/setup.py", line 192, in <module>
     File "/usr/lib/python3.5/distutils/core.py", line 163, in setup
       raise SystemExit("error: " + str(msg))
   SystemExit: error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
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   During handling of the above exception, another exception occurred:
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   Traceback (most recent call last):
     File "<string>", line 1, in <module>
     File "/tmp/pip-build-vuihdm69/argon2-cffi/setup.py", line 160, in <module>
       extras_require=EXTRAS_REQUIRE,
     File "/usr/lib/python3.5/distutils/core.py", line 108, in setup
       _setup_distribution = dist = klass(attrs)
     File "/usr/lib/python3/dist-packages/setuptools/dist.py", line 269, in __init__
       self.fetch_build_eggs(attrs['setup_requires'])
     File "/usr/lib/python3/dist-packages/setuptools/dist.py", line 313, in fetch_build_eggs
       replace_conflicting=True,
     File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 826, in resolve
       dist = best[req.key] = env.best_match(req, ws, installer)
     File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 1092, in best_match
       return self.obtain(req, installer)
     File "/usr/lib/python3/dist-packages/pkg_resources/__init__.py", line 1104, in obtain
       return installer(requirement)
     File "/usr/lib/python3/dist-packages/setuptools/dist.py", line 380, in fetch_build_egg
       return cmd.easy_install(req)
     File "/usr/lib/python3/dist-packages/setuptools/command/easy_install.py", line 663, in easy_install
       return self.install_item(spec, dist.location, tmpdir, deps)
     File "/usr/lib/python3/dist-packages/setuptools/command/easy_install.py", line 693, in install_item
       dists = self.install_eggs(spec, download, tmpdir)
     File "/usr/lib/python3/dist-packages/setuptools/command/easy_install.py", line 873, in install_eggs
       return self.build_and_install(setup_script, setup_base)
     File "/usr/lib/python3/dist-packages/setuptools/command/easy_install.py", line 1101, in build_and_install
       self.run_setup(setup_script, setup_base, args)
     File "/usr/lib/python3/dist-packages/setuptools/command/easy_install.py", line 1089, 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
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   ----------------------------------------