Gsutil fails decoding service account key

I'm trying to use gsutil to upload files to gcs and it's running into a bad base64 error from OpenSSL (version 0.13.1):
`OpenSSL.crypto.Error: [('PEM routines', 'PEM_read_bio', 'bad base64 decode')]` (full stacktrace in the attachment)

I tried executing the same operation with pyOpenSSL 0.19 and it was decoding without errors. Moreover, using the service key to authenticate with gcloud worked and I was able to access all clusters etc, so my guess it's a local issue with gsutil.

Thanks for your time
[stacktrace.txt](https://github.com/GoogleCloudPlatform/gsutil/files/3635978/stacktrace.txt)