Bump pytest from 6.1.2 to 6.2.2 (#433)

* Bump pytest from 6.1.2 to 6.2.2

Bumps [pytest](https://github.com/pytest-dev/pytest) from 6.1.2 to 6.2.2.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@6.1.2...6.2.2)

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

* Use Python 3.7 in tests 

Since that's our runtime environment.

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>
Co-authored-by: Mariatta Wijaya <[email protected]>

Author: dependabot-preview[bot]

.travis.yml

@@ -1,8 +1,6 @@
 language: python
 cache: pip
 python:
-  - 3.6
-  - 3.6-dev
   - 3.7-dev
   # - nightly
 

dev-requirements.txt

@@ -1,6 +1,6 @@
 -r requirements.txt
 coverage
-pytest==6.1.2
+pytest==6.2.2
 pytest-asyncio==0.14.0
 pytest-aiohttp==0.3.0
 pytest-cov==2.11.1