Update sign_cryptography.py

[GeekTan]

fix python3 read() return is utf-8 to ascii

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[coveralls]

Coverage decreased (-0.1%) to 43.492% when pulling 2d9ca8b on GeekTan:master into 0e50795 on google:master.

[coveralls]

Coverage decreased (-0.1%) to 43.492% when pulling 2d9ca8b on GeekTan:master into 0e50795 on google:master.