Bump python-slugify from 3.0.2 to 3.0.3

Bumps [python-slugify](https://github.com/un33k/python-slugify) from 3.0.2 to 3.0.3.
- [Release notes](https://github.com/un33k/python-slugify/releases)
- [Changelog](https://github.com/un33k/python-slugify/blob/master/CHANGELOG.md)
- [Commits](un33k/python-slugify@3.0.2...3.0.3)

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

requirements/base.txt

@@ -37,7 +37,7 @@ pandas==0.25.0
 Pillow==6.0.0  # https://github.com/python-pillow/Pillow
 PyHamcrest==1.9.0
 python-coveralls==2.9.2
-python-slugify==3.0.2  # https://github.com/un33k/python-slugify
+python-slugify==3.0.3  # https://github.com/un33k/python-slugify
 pytz==2019.1  # https://github.com/stub42/pytz
 PyYAML==5.1.1
 redis==3.3.5  # https://github.com/antirez/redis