Bump coverage from 4.5.3 to 4.5.4

Bumps [coverage](https://github.com/nedbat/coveragepy) from 4.5.3 to 4.5.4.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-4.5.3...coverage-4.5.4)

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

Author: dependabot-preview[bot]

test-requirements.txt

@@ -12,7 +12,7 @@ atomicwrites==1.3.0       # via pytest
 attrs==19.1.0
 backcall==0.1.0           # via ipython
 cffi==1.12.3              # via cryptography
-coverage==4.5.3           # via pytest-cov
+coverage==4.5.4           # via pytest-cov
 cryptography==2.7         # via pyopenssl, trustme
 decorator==4.4.0          # via ipython, traitlets
 entrypoints==0.3          # via flake8