Raised when errors occur during PKey#sign or PKey#verify.

Before version 4.0.0, OpenSSL::PKey::PKeyError had the following subclasses. These subclasses have been removed and the constants are now defined as aliases of OpenSSL::PKey::PKeyError.

• OpenSSL::PKey::DHError

• OpenSSL::PKey::DSAError

• OpenSSL::PKey::ECError

• OpenSSL::PKey::RSAError