SMIME signing bug

Clear signing large (>3Mb) SMIME messages from M2Crypto hangs python.

1.  A test run with debug print statements in my code and in
     M2Crypto.SMIME.py:

     time ./signer.py newreq_nopass.pem newcert.pem 21131.eml
21131_signed.eml

     setup
     BIO.MemoryBuffer(text)
     self._smime.sign
     m2.pkcs7_sign0 called
     [1]   Terminated              ./signer.py newreq_nopass.pem
newcert.pem 21131.eml 21131_signed.eml

     [2]+  Stopped                 ./signer.py newreq_nopass.pem
newcert.pem 21131.eml 21131_signed.eml

     real    0m26.028s
     user    0m0.000s
     sys     0m0.000s

     I had to kill %1 the backgrounded job, as ^C did nothing. I have
     tried leaving the process running for 15 minutes, and it just
     stays there eating a bit more memory each second.

2.  If I sign the same messages from openssl:

     time openssl smime -sign -in 21131.eml -out 21131_signed.eml
-signer newcert.pem -inkey newreq_nopass.pem

     real    0m0.671s
     user    0m0.538s
     sys     0m0.100s

3.  My same code using M2Crypto on a small message:

     time ./signer.py newreq_nopass.pem newcert.pem test.eml test_signed.eml

     setup
     BIO.MemoryBuffer(text)
     self._smime.sign
     m2.pkcs7_sign0 called
     BIO.MemoryBuffer(text)
     self._smime.write
     self._parser.parsestr

     real    0m0.390s
     user    0m0.197s
     sys     0m0.030s

the message sizes are:

ls -l *eml
-rw-r--r--    1 ludo     ludo      4777277 Jul  1 11:52 21131.eml
-rw-r--r--    1 ludo     ludo      4841919 Jul  1 12:20 21131_signed.eml
-rw-r--r--    1 ludo     ludo         6026 Jun 23 00:27 test.eml
-rw-r--r--    1 ludo     ludo         8730 Jul  1 12:21 test_signed.eml

I really need smime signing to work, should I wrap openssl's smime
command from python or is there a chance this will be fixed in M2Crypto?

Thanks

Ludo