Bump python-dateutil from 2.6.1 to 2.8.1

Bumps [python-dateutil](https://github.com/dateutil/dateutil) from 2.6.1 to 2.8.1.
- [Release notes](https://github.com/dateutil/dateutil/releases)
- [Changelog](https://github.com/dateutil/dateutil/blob/master/NEWS)
- [Commits](https://github.com/dateutil/dateutil/compare/2.6.1...2.8.1)

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

requirements.txt

@@ -18,7 +18,7 @@ ns1-python==0.13.0
 ovh==0.4.8
 pycountry-convert==0.7.2
 pycountry==19.8.18
-python-dateutil==2.6.1
+python-dateutil==2.8.1
 requests==2.22.0
 s3transfer==0.1.13
 setuptools==40.3.0

setup.py

@@ -74,7 +74,7 @@ setup(
         'pycountry>=19.8.18',
         'pycountry-convert>=0.7.2',
         # botocore doesn't like >=2.7.0 for some reason
-        'python-dateutil>=2.6.0,<2.7.0',
+        'python-dateutil>=2.6.0,<2.9.0',
         'requests>=2.20.0'
     ],
     license='MIT',