Bump coverage from 5.0.2 to 5.0.3

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.0.2 to 5.0.3.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-5.0.2...coverage-5.0.3)

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

requirements.txt

@@ -1,4 +1,4 @@
-coverage==5.0.2
+coverage==5.0.3
 Django==1.11.26 # pyup: <2.0
 django-debug-toolbar==2.1
 docutils==0.16