I'm trying to install the Python M2Crypto package into a virtualenv on an x86_64 RHEL 6.1 machine. This process invokes swig, which fails with the following error:

$ virtualenv -q --no-site-packages venv
$ pip install -E venv M2Crypto==0.20.2
Downloading/unpacking M2Crypto==0.20.2
  Downloading M2Crypto-0.20.2.tar.gz (412Kb): 412Kb  downloaded
  Running setup.py egg_info for package M2Crypto
Installing collected packages: M2Crypto
  Running setup.py install for M2Crypto
    building 'M2Crypto.__m2crypto' extension
    swigging SWIG/_m2crypto.i to SWIG/_m2crypto_wrap.c
    swig -python -I/usr/include/python2.6 -I/usr/include -includeall -o SWIG/_m2crypto_wrap.c SWIG/_m2crypto.i
    /usr/include/openssl/opensslconf.h:31: Error: CPP #error ""This openssl-devel package does not work your architecture?"". Use the -cpperraswarn option to continue swig processing.
    error: command 'swig' failed with exit status 1
    Complete output from command /home/lorin/venv/bin/python -c "import setuptools;__file__='/home/lorin/venv/build/M2Crypto/setup.py';exec(compile(open(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --single-version-externally-managed --record /tmp/pip-BFiNtU-record/install-record.txt --install-headers /home/lorin/venv/include/site/python2.6:

I've got OpenSSL 1.0.0 installed via RPM packages from RedHat.

The part of /usr/include/openssl/opensslconf.h that causes the error looks like this:

#if defined(__i386__)
#include "opensslconf-i386.h"
#elif defined(__ia64__)
#include "opensslconf-ia64.h"
#elif defined(__powerpc64__)
#include "opensslconf-ppc64.h"
#elif defined(__powerpc__)
#include "opensslconf-ppc.h"
#elif defined(__s390x__)
#include "opensslconf-s390x.h"
#elif defined(__s390__)
#include "opensslconf-s390.h"
#elif defined(__sparc__) && defined(__arch64__)
#include "opensslconf-sparc64.h"
#elif defined(__sparc__)
#include "opensslconf-sparc.h"
#elif defined(__x86_64__)
#include "opensslconf-x86_64.h"
#else
#error "This openssl-devel package does not work your architecture?"
#endif

gcc has the right variable defined:

$ echo | gcc -E -dM - | grep x86_64
#define __x86_64 1
#define __x86_64__ 1

But apparenty swig doesn't, since this is the line that's failing:

swig -python -I/usr/include/python2.6 -I/usr/include -includeall -o \
  SWIG/_m2crypto_wrap.c SWIG/_m2crypto.i

Is there a way to fix this by changing something in my system configuration? M2Crypto gets installed in a virtualenv as part of a larger script I don't control, so avoiding mucking around with the M2Crypto files would be a good thing.