gcloud compute ssl-certificates create mysertificatee \
--certificate mySite.com.csr \
--private-key mySite.com.key

--certificate的参数应为证书，即mySite.com.pem.取而代之的是CSR mySite.com.csr.

The argument for --certificate should be the certificate, i.e. mySite.com.pem. Instead the CSR mySite.com.csr was given.