Pin tzlocal between 4.0 and 5.0

As noted in O365#967

Author: Alejandro Casanovas

setup.py

@@ -36,7 +36,7 @@ def read(fname):
     'requests_oauthlib>=1.2.0',
     'python-dateutil>=2.7',
     'pytz>=2018.5',
-    'tzlocal>=4.0',
+    'tzlocal>=4.0,<5.0',
     'beautifulsoup4>=4.0.0',
     'stringcase>=1.2.0'
 ]