Warning message when with notebook()

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After running notebook(), the following warning. I read a few posts online regarding this with past version. Any insights on this version?

/usr/local/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)