MNT: Replace uses of drop_vars with drop

drop_vars is only available on xarray 0.14.0

tests/calc/test_cross_sections.py

@@ -148,7 +148,7 @@ def test_distances_from_cross_section_given_xy(test_cross_xy):
 def test_distances_from_cross_section_given_bad_coords(test_cross_xy):
     """Ensure an AttributeError is raised when the cross section lacks neeed coordinates."""
     with pytest.raises(AttributeError):
-        distances_from_cross_section(test_cross_xy['u_wind'].drop_vars('x'))
+        distances_from_cross_section(test_cross_xy['u_wind'].drop('x'))
 
 
 def test_latitude_from_cross_section_given_lat(test_cross_lonlat):

tests/calc/test_kinematics.py

@@ -1035,9 +1035,10 @@ def data_4d():
     data = xr.open_dataset(get_test_data('irma_gfs_example.nc', False))
     data = data.metpy.parse_cf()
     data['Geopotential_height_isobaric'].attrs['units'] = 'm'
-    subset = data.drop_vars((
+    subset = data.drop((
         'LatLon_361X720-0p25S-180p00E', 'Vertical_velocity_pressure_isobaric', 'isobaric1',
         'Relative_humidity_isobaric', 'reftime'
+
     )).sel(
         latitude=[46., 44., 42., 40.],
         longitude=[262., 267., 272., 277.],

tests/test_xarray.py

@@ -57,7 +57,7 @@ def test_var_multidim_full(test_ds):
 @pytest.fixture
 def test_var_multidim_no_xy(test_var_multidim_full):
     """Provide a variable with multidimensional lat/lon coords but without x/y coords."""
-    return test_var_multidim_full.drop_vars(['y', 'x'])
+    return test_var_multidim_full.drop(['y', 'x'])
 
 
 def test_projection(test_var):
@@ -474,7 +474,7 @@ def test_coordinates_identical_true(test_ds_generic):
 
 def test_coordinates_identical_false_number_of_coords(test_ds_generic):
     """Test coordinates identical method when false due to number of coordinates."""
-    other_ds = test_ds_generic.drop_vars('e')
+    other_ds = test_ds_generic.drop('e')
     assert not test_ds_generic['test'].metpy.coordinates_identical(other_ds['test'])