wcst_import: more informative error message

[Dimitar Misev]

These cases fail on my system:

test.sh: Test case: /home/dimitar/rasdaman/community/src/systemtest/testcases_services/test_all_wcst_import/testdata/grib_irregular_1_message...failed.
test.sh: Reason: Failed importing coverage.
test.sh: ----------------------------------------------------------------------
test.sh: 
test.sh: Test case: /home/dimitar/rasdaman/community/src/systemtest/testcases_services/test_all_wcst_import/testdata/grib_regular_5_messages...failed.
test.sh: Reason: Failed importing coverage.
test.sh: ----------------------------------------------------------------------
test.sh: 
test.sh: Test case: /home/dimitar/rasdaman/community/src/systemtest/testcases_services/test_all_wcst_import/testdata/grib_regular_5_messages_pixel_is_point...failed.
test.sh: Reason: Failed importing coverage.
test.sh: ----------------------------------------------------------------------
test.sh: 
test.sh: Test case: /home/dimitar/rasdaman/community/src/systemtest/testcases_services/test_all_wcst_import/testdata/test_ecmwf_grib_1_aggregated_irregular_axis...failed.
test.sh: Reason: Failed importing coverage.
test.sh: ----------------------------------------------------------------------
test.sh: 
test.sh: Test case: /home/dimitar/rasdaman/community/src/systemtest/testcases_services/test_all_wcst_import/testdata/test_ecmwf_grib_float_coefficients_comparison...failed.
test.sh: Reason: Failed importing coverage.
test.sh: ----------------------------------------------------------------------
test.sh: 
test.sh: Test case: /home/dimitar/rasdaman/community/src/systemtest/testcases_services/test_all_wcst_import/testdata/wcs_ecmwf_grib_2_aggregated_irregular_axes...failed.
test.sh: Reason: Failed importing coverage.
test.sh: ----------------------------------------------------------------------

I tested manually for grib_irregular_1_message (in the output directory there's no logs..):

Runtime error: Cannot import GRIB data, please install pygrib first (sudo pip install pygrib).

pygrib is installed, however

$ sudo pip install pygrib
Requirement already satisfied: pygrib in /usr/local/lib/python2.7/dist-packages

then I tried this

>>> import pygrib
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pygrib.pyx", line 184, in init pygrib (pygrib.c:35163)
ImportError: either pyproj or basemap required

to fix it I needed to

sudo apt-get install libpython-dev
sudo pip install pyproj

tl;dr:

1. The missing pygrib error message should be improved. The exception message (which says pyproj is missing) should not be lost.
2. The wcst_import tests output directory should contain logs of running wcst_import