PowmInsecureWarning, how do I rebuild using libgmp >= 5

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1st Awesome work !! thank you very much !! Quite a task getting all that external code working together.

Successfully built 6.4.1 on an 8GB iMac with no problems in 3 hour 6 minutes. I forgot to use the multiprocessor setting.

Only issue is when starting notebook() I get this warning: /sage-6.4.1/local/lib/python2.7/site-packages/Crypto/Util/number.py:57: PowmInsecureWarning: Not using mpz_powm_sec. You should rebuild using libgmp >= 5 to avoid timing attack vulnerability. _warn("Not using mpz_powm_sec. You should rebuild using libgmp >= 5 to avoid timing attack vulnerability.", PowmInsecureWarning)

How do I update this.

thanks