python-ecdsa vulnerable to Minerva attack on P-256

The `ecdsa` PyPI package is a pure Python implementation of ECC (Elliptic Curve Cryptography) with support for ECDSA (Elliptic Curve Digital Signature Algorithm), EdDSA (Edwards-curve Digital Signature Algorithm) and ECDH (Elliptic Curve Diffie-Hellman). Versions 0.18.0 and prior are vulnerable to the Minerva attack. As of time of publication, no known patched version exists.