wcst_import - FIX - check if python-dateutil exists before it runs

[Bang Pham Huu]

To avoid the stack trace like below:

wcst_import.sh GSM_900.json

wcst_import.sh: rasdaman v10.1.0 build

Traceback (most recent call last):

  File "/opt/rasdaman/share/rasdaman/wcst_import/wcst_import.py", line 37, in <module>

    from master.recipe.recipe_registry import RecipeRegistry

  File "/opt/rasdaman/share/rasdaman/wcst_import/master/recipe/recipe_registry.py", line 31, in <module>

    from master.evaluator.evaluator_slice_factory import EvaluatorSliceFactory

  File "/opt/rasdaman/share/rasdaman/wcst_import/master/evaluator/evaluator_slice_factory.py", line 25, in <module>

    from master.evaluator.evaluator_slice import GDALEvaluatorSlice

  File "/opt/rasdaman/share/rasdaman/wcst_import/master/evaluator/evaluator_slice.py", line 24, in <module>

    from util.file_util import File

  File "/opt/rasdaman/share/rasdaman/wcst_import/util/file_util.py", line 28, in <module>

    from config_manager import ConfigManager

  File "/opt/rasdaman/share/rasdaman/wcst_import/config_manager.py", line 24, in <module>

    from master.request.wcst import WCSTExecutor

  File "/opt/rasdaman/share/rasdaman/wcst_import/master/request/wcst.py", line 28, in <module>

    from util.log import log, make_bold

  File "/opt/rasdaman/share/rasdaman/wcst_import/util/log.py", line 30, in <module>

    from util.time_util import DateTimeUtil

  File "/opt/rasdaman/share/rasdaman/wcst_import/util/time_util.py", line 33, in <module>

    from lib.arrow import api as arrow

  File "/opt/rasdaman/share/rasdaman/wcst_import/lib/arrow/__init__.py", line 3, in <module>

    from .arrow import Arrow

  File "/opt/rasdaman/share/rasdaman/wcst_import/lib/arrow/arrow.py", line 10, in <module>

    from dateutil import tz as dateutil_tz