Log Message:
py-arrow: updated to 0.15.8

0.15.8
- [WARN] arrow will **drop support** for Python 2.7 and 3.5 in the 1.0.0 release \ 
in late September. The 0.15.x and 0.16.x releases are the last to support Python \ 
2.7 and 3.5.
- [NEW] Added ``humanize`` week granularity translation for Czech.
- [FIX] ``arrow.get`` will now pick sane defaults when weekdays are passed with \ 
particular token combinations.
- [INTERNAL] Moved arrow to an organization. The repo can now be found `here \ 
<https://github.com/arrow-py/arrow>`_.
- [INTERNAL] Started issuing deprecation warnings for Python 2.7 and 3.5.
- [INTERNAL] Added Python 3.9 to CI pipeline.