Hi,

gcloud/credentials/generate_signed_url still expects to find the private key in _private_key_pkcs8_pem but it has been wrapped by the signer now. I can set it myself as has been done in the classmethod constructors, but this seems the wrong place to be doing this. The default __init__ should be setting this not classmethods as others, like me, may not be using them.

Should the key really be in both_private_key_pkcs8_pem and signer? This looks fragile, and indeed has broken for me.

Thanks