Hi
Just to point it out, I think that the two stack overflow posts you link are not exactly relevant to your issue, as they are 2 and 4 year old respectively. I don't believe the appcfg.py tool has been broken for that long.
Did you update to gcloud or are you staying on the php standalone SDK on purpose? Because earlier this week we deprecated the standalone SDKs to move to gcloud.
I'd test with a fresh python install and the newest gcloud version, making sure there's NOTHING "polluting" your PATH, so to speak.
Cheers