build(deps): bump pytest from 5.1.2 to 5.2.1

Bumps [pytest](https://github.com/pytest-dev/pytest) from 5.1.2 to 5.2.1.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@5.1.2...5.2.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

travis/requirements.txt

@@ -1,5 +1,5 @@
 freezegun==0.3.12
-pytest==5.1.2
+pytest==5.2.1
 pytest-asyncio==0.10.0
 responses==0.10.6
 pytest-cov==2.8.1