Fix test-skipping logic and remove 'dummy' from warning

Author: spencerkclark

xarray/coding/times.py

@@ -183,7 +183,7 @@ def decode_cf_datetime(num_dates, units, calendar=None, use_cftime=None):
                 if calendar in _STANDARD_CALENDARS:
                     warnings.warn(
                         'Unable to decode time axis into full '
-                        'numpy.datetime64 objects, continuing using dummy '
+                        'numpy.datetime64 objects, continuing using '
                         'cftime.datetime objects instead, reason: dates out '
                         'of range', SerializationWarning, stacklevel=3)
             else:

xarray/tests/test_backends.py

@@ -3467,6 +3467,7 @@ def test_source_encoding_always_present():
             assert ds.encoding['source'] == tmp
 
 
+@requires_scipy_or_netCDF4
 @pytest.mark.parametrize('calendar', _STANDARD_CALENDARS)
 def test_use_cftime_standard_calendar_default_in_range(calendar):
     x = [0, 1]
@@ -3497,6 +3498,7 @@ def test_use_cftime_standard_calendar_default_in_range(calendar):
 
 
 @requires_cftime
+@requires_scipy_or_netCDF4
 @pytest.mark.parametrize('calendar', _STANDARD_CALENDARS)
 @pytest.mark.parametrize('units_year', [1500, 2500])
 def test_use_cftime_standard_calendar_default_out_of_range(
@@ -3530,6 +3532,7 @@ def test_use_cftime_standard_calendar_default_out_of_range(
 
 
 @requires_cftime
+@requires_scipy_or_netCDF4
 @pytest.mark.parametrize('calendar', _ALL_CALENDARS)
 @pytest.mark.parametrize('units_year', [1500, 2000, 2500])
 def test_use_cftime_true(
@@ -3563,6 +3566,7 @@ def test_use_cftime_true(
             assert not record
 
 
+@requires_scipy_or_netCDF4
 @pytest.mark.parametrize('calendar', _STANDARD_CALENDARS)
 def test_use_cftime_false_standard_calendar_in_range(calendar):
     x = [0, 1]
@@ -3592,6 +3596,7 @@ def test_use_cftime_false_standard_calendar_in_range(calendar):
             assert not record
 
 
+@requires_scipy_or_netCDF4
 @pytest.mark.parametrize('calendar', _STANDARD_CALENDARS)
 @pytest.mark.parametrize('units_year', [1500, 2500])
 def test_use_cftime_false_standard_calendar_out_of_range(calendar, units_year):
@@ -3610,6 +3615,7 @@ def test_use_cftime_false_standard_calendar_out_of_range(calendar, units_year):
             open_dataset(tmp_file, use_cftime=False)
 
 
+@requires_scipy_or_netCDF4
 @pytest.mark.parametrize('calendar', _NON_STANDARD_CALENDARS)
 @pytest.mark.parametrize('units_year', [1500, 2000, 2500])
 def test_use_cftime_false_nonstandard_calendar(calendar, units_year):