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](pytest-dev/py@1.8.1...1.9.0)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

build/test-requirements.txt

@@ -11,7 +11,7 @@ prospector==1.2.0 # Last version of prospector with Python 2.7 support
 pydocstyle
 nose
 pytest==4.6.9 # Last version of pytest with Python 2.7 support
-py==1.8.1
+py==1.9.0
 rope
 flask
 django