@JonB I finally got it working.
I have working Google People API environment on anaconda3 in my Linux box. Archived google* files and directories in ~/anaconda3/lib/python3.7/site-packages, brought the tar ball in pythonista3 folder in iCloud, and restored in site-packages directory. To make it working, I also needed to PIP install six and httplib2. This time StaSh did the job.
Needless to say you've got to prepare credentials.json and put in in your working directory.