Bump pytz from 2019.1 to 2019.2

Bumps [pytz](https://github.com/stub42/pytz) from 2019.1 to 2019.2.
- [Release notes](https://github.com/stub42/pytz/releases)
- [Commits](stub42/pytz@release_2019.1...release_2019.2)

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

requirements.txt

@@ -98,7 +98,7 @@ inflection<=0.3.1
 jdcal==1.4.1
 mock<4.0.0
 python-dateutil==2.8.0
-pytz==2019.1
+pytz==2019.2
 requests==2.22.0
 simplejson==3.16.0
 timeout-decorator==0.4.1