Error installing graphite carbon

Question

I am trying to install graphite carbon (version 0.9.15) requirements by running the following command:

pip --proxy http://<proxy-host>:<proxy-port> install -r requirements.txt

The requirements.txt has the following contents:

Twisted>=13.2.0
git+git://github.com/graphite-project/[email protected]#egg=whisper
mocker==1.1.1
mock

However when I run the above command I get:

Collecting Twisted>=13.2.0 (from -r requirements.txt (line 1))
  Using cached Twisted-16.6.0.tar.bz2
    Complete output from command python setup.py egg_info:
    Download error on https://pypi.python.org/simple/incremental/: [Errno 101] Network is unreachable -- Some packages may not be found!
    Couldn't find index page for 'incremental' (maybe misspelled?)
    Download error on https://pypi.python.org/simple/: [Errno 101] Network is unreachable -- Some packages may not be found!
    No local packages or download links found for incremental>=16.10.1
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-build-6klpfA/Twisted/setup.py", line 21, in <module>
        setuptools.setup(**_setup["getSetupArgs"]())
      File "/usr/lib64/python2.7/distutils/core.py", line 111, in setup
        _setup_distribution = dist = klass(attrs)
      File "/opt/graphite/lib/python2.7/site-packages/setuptools/dist.py", line 269, in __init__
        self.fetch_build_eggs(attrs['setup_requires'])
      File "/opt/graphite/lib/python2.7/site-packages/setuptools/dist.py", line 313, in fetch_build_eggs
        replace_conflicting=True,
      File "/opt/graphite/lib/python2.7/site-packages/pkg_resources/__init__.py", line 827, in resolve
        dist = best[req.key] = env.best_match(req, ws, installer)
      File "/opt/graphite/lib/python2.7/site-packages/pkg_resources/__init__.py", line 1072, in best_match
        return self.obtain(req, installer)
      File "/opt/graphite/lib/python2.7/site-packages/pkg_resources/__init__.py", line 1084, in obtain
        return installer(requirement)
      File "/opt/graphite/lib/python2.7/site-packages/setuptools/dist.py", line 380, in fetch_build_egg
        return cmd.easy_install(req)
      File "/opt/graphite/lib/python2.7/site-packages/setuptools/command/easy_install.py", line 634, in easy_install
        raise DistutilsError(msg)
    distutils.errors.DistutilsError: Could not find suitable distribution for Requirement.parse('incremental>=16.10.1')

The strange thing is that when accessing the https://pypi.python.org/simple/incremental/ index page through the proxy I can see there is an incremental-16.10.1.tar.gz package.

What could be the issue here? Is this something network-related problem or a pip-related one?