Bump py from 1.8.1 to 1.9.0

Bumps [py](https://github.com/pytest-dev/py) from 1.8.1 to 1.9.0.
- [Release notes](https://github.com/pytest-dev/py/releases)
- [Changelog](https://github.com/pytest-dev/py/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/pytest-dev/py/compare/1.8.1...1.9.0)

requirements.txt

@@ -17,7 +17,7 @@ outlier-utils==0.0.3
 packaging==20.4
 pandas==1.0.1
 pluggy==0.13.1
-py==1.8.1
+py==1.9.0
 pyarrow==1.0.0
 pyparsing==2.4.6
 pytest-lazy-fixture==0.6.3