Log Message:
py-asciinema: update to 2.1.0.

## 2.1.0 (2021-10-02)

* Ability to pause/resume terminal capture with `C-\` key shortcut
* Desktop notifications - only for the above pause feature at the moment
* Removed dependency on tput/ncurses (thanks @arp242 / Martin Tournoij!)
* ASCIINEMA_REC env var is back (thanks @landonb / Landon Bouma!)
* Terminal answerbacks (CSI 6 n) in `asciinema cat` are now hidden (thanks \ 
@djpohly / Devin J. Pohly!)
* Codeset detection works on HP-UX now (thanks @michael-o / Michael Osipov!)
* Attempt at recording to existing file suggests use of `--overwrite` option now
* Upload for users with very long `$USER` is fixed
* Added official support for Python 3.8 and 3.9
* Dropped official support for EOL-ed Python 3.4 and 3.5
* Internal refactorings