[Distutils] PyPI download issues from Rackspace Cloud

[Marius Gedminas]

I recently spin up a Windows VM on Rackspace Cloud.  I'm seeing a very
weird problem: downloads from PyPI fail with checksum errors,
nondeterministically.

Sometimes it's a md5 hash mismatch error from pip[1].  Sometimes the
error is a CRC error deep in the gzip module.  It's not only pip -- I've
seen this error from virtualenv[2], I've seen it from get-pip.py.

[1] https://jenkins.gedmin.as/job/restview-on-windows/1/console
    https://jenkins.gedmin.as/job/restview-on-windows/2/console
    https://jenkins.gedmin.as/job/restview-on-windows/3/console
    https://jenkins.gedmin.as/job/check-manifest-on-windows/11/console

[2] https://jenkins.gedmin.as/job/check-manifest-on-windows/7/console
    https://jenkins.gedmin.as/job/check-manifest-on-windows/6/console

The error is sporadic and tends to go away (and come back) on retries
(look at the restview-on-windows jobs: first pip install mock fails,
then succeeds, then fails again on next retry).

I haven't encountered any download troubles with Firefox.  In fact
that's how I got 'pip install tox' to work in the end -- pypi downloads
of virtualenv/py libraries kept failing, so I downloaded the tarballs
with Firefox and pip installed them from local files.

I've ran

  curl https://pypi.python.org/packages/source/v/virtualenv/virtualenv-1.10.1.tar.gz | md5sum -

like 10 times and got the same (correct) md5 hash each time.  Meanwhile

  unset PIP_DOWNLOAD_CACHE
  rm -f virtualenv-1.10.1.tar.gz && pip install -d . virtualenv

fails with a bad md5hash error 9 times out of 10.  Curiously, it's the
same bad hash every time: 20cf17baaf2126f99d6f652831f82d75.

I used http://www.python.org/ftp/python/2.7.6/python-2.7.6.msi to
install Python on this Windows 2012 server (64-bit OS, 32-bit Python).

Any ideas?

Marius Gedminas
-- 
IBM motto: "We found five vowels hiding in a corner, and we used
them _all_ for the 'eieio' instruction so that we wouldn't have to use
them anywhere else"
		-- Linus Torvalds
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