Prevent ImportError if pytz is not installed.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@24742 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/Utils.py

@@ -2598,7 +2598,10 @@ def sleep(t=5):
 
 def getCommonTimeZoneList():
   """ Get common (country/capital(major cities) format) timezones list """
-  from pytz import common_timezones
+  try:
+    from pytz import common_timezones
+  except ImportError:
+    return []
   return common_timezones