Bump codecov from 2.0.15 to 2.0.16

Bumps [codecov](https://github.com/codecov/codecov-python) from 2.0.15 to 2.0.16.
- [Release notes](https://github.com/codecov/codecov-python/releases)
- [Changelog](https://github.com/codecov/codecov-python/blob/master/CHANGELOG.md)
- [Commits](codecov/codecov-python@v2.0.15...v2.0.16)

---
updated-dependencies:
- dependency-name: codecov
  dependency-type: direct:development
...

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

Author: dependabot[bot]

dev_requirements.txt

@@ -3,4 +3,4 @@ pylint==1.9.4; python_version < '3.0'
 pylint==2.6.0; python_version > '3.5'
 requests-mock==1.5.2
 collective.checkdocs==0.2
-codecov==2.0.15
+codecov==2.0.16