Bump pytest from 3.2.5 to 5.3.5

Bumps [pytest](https://github.com/pytest-dev/pytest) from 3.2.5 to 5.3.5.
- [Release notes](https://github.com/pytest-dev/pytest/releases)
- [Changelog](https://github.com/pytest-dev/pytest/blob/master/CHANGELOG.rst)
- [Commits](pytest-dev/pytest@3.2.5...5.3.5)

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

Author: dependabot-preview[bot]

requirements-test.txt

@@ -5,7 +5,7 @@
 # pin all of our direct dependencies
 tox==3.14.5
 flake8==3.7.9
-pytest==3.10.1,<4  # see https://github.com/html5lib/html5lib-python/pull/429
+pytest==5.3.5  # see https://github.com/html5lib/html5lib-python/pull/429
 coverage==5.0.3
 pytest-expect==1.1.0
 mock==3.0.5