games/py-mnemosyne: fix runtime error

[lbartoletti]

Summary

Latest version of games/py-mnemosyne requires new dependencies. The patch adds the missing dependencies:

• audio/py-gtts
• security/py-gtts-token (required by audio/py-gtts)
• textproc/py-googletrans

The games/py-mnemosyne port needs to be limited to Python 3.7+ to keep the dependency chains intact. This is because textproc/py-googletrans depends on www/py-httpx which is only for Python 3.7+ .

We definitely need also to merge whole changes to the 2020Q3 branch as the port is broken there at the moment.

Thanks kai@

Test Plan

• poudriere (12/13 i386/amd64)
• runtime tests by kai@, me and [e-mail]

[tcberner]

Ship it. Don't forget to add MFH: 2020Q3, if you intend to mfh this :)