Bump python-dotenv from 0.13.0 to 0.15.0

Bumps [python-dotenv](https://github.com/theskumar/python-dotenv) from 0.13.0 to 0.15.0.
- [Release notes](https://github.com/theskumar/python-dotenv/releases)
- [Changelog](https://github.com/theskumar/python-dotenv/blob/master/CHANGELOG.md)
- [Commits](theskumar/python-dotenv@v0.13.0...v0.15.0)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

Pipfile.lock

@@ -1,6 +1,7 @@
-asgiref==3.2.10
-Django==3.1.2
-mysqlclient==2.0.1
-python-dotenv==0.14.0
-pytz==2020.1
-sqlparse==0.3.1
+-i https://pypi.org/simple/
+asgiref==3.3.1
+django==3.0.7
+mysqlclient==1.4.6
+python-dotenv==0.15.0
+pytz==2020.4
+sqlparse==0.4.1