[issue2551030] Roundup fails to start if pytz to access Olson timezone database not installed

New submission from John Rouillard:

When running roundup, the Olson timezone database (pytz) is supposed to 
be optional. However the configuration.py file uses:

        (TimezoneOption, "timezone", "UTC", "Default timezone offset,"
            " applied when user's timezone is not set.",
            ["DEFAULT_TIMEZONE"]),

in ths

  SETTINGS = (
      ("main", (

tuple definition. This raises an exception when trying to parse UTC
if pytz is not installed. I think the fix it to set a variable
for the setting:

  try:
    import pytz
    timezone=  (TimezoneOption, "timezone", "UTC",
                "Default timezone offset,"
            " applied when user's timezone is not set.",
            ["DEFAULT_TIMEZONE"])
  except ImportError:
    timezone = (TimezoneOption, "timezone", "0",
            "Default timezone offset,"
            " applied when user's timezone is not set.",
            ["DEFAULT_TIMEZONE"])

then replace the entry in the tuple with timezone. I think this would 
work, but I am not sure.

----------
components: Infrastructure
keywords: Effort-Low
messages: 6386
nosy: rouilj
priority: high
severity: major
status: new
title: Roundup fails to start if pytz to access Olson timezone database not installed
type: crash
versions: 1.6, devel

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