[ci] temporarily pin scipy version and fix Python linting error (#5398)

.ci/test.sh

@@ -120,22 +120,21 @@ fi
 
 # temporary fix for https://github.com/microsoft/LightGBM/issues/5390
 if [[ $PYTHON_VERSION == "3.7" ]]; then
-    DASK_DEPENDENCIES="dask distributed"
+    DEPENDENCIES="dask distributed"
 else
-    DASK_DEPENDENCIES="dask=2022.7.0 distributed=2022.7.0"
+    DEPENDENCIES="dask=2022.7.0 distributed=2022.7.0 scipy<1.9"
 fi
 
 conda install -q -y -n $CONDA_ENV \
     cloudpickle \
-    ${DASK_DEPENDENCIES} \
+    ${DEPENDENCIES} \
     joblib \
     matplotlib \
     numpy \
     pandas \
     psutil \
     pytest \
-    scikit-learn \
-    scipy || exit -1
+    scikit-learn || exit -1
 
 # python-graphviz has to be installed separately to prevent conda from downgrading to pypy
 conda install -q -y -n $CONDA_ENV \

python-package/lightgbm/basic.py

@@ -1507,7 +1507,7 @@ class Dataset:
                 for cat_alias in _ConfigAliases.get("categorical_feature"):
                     if cat_alias in params:
                         # If the params[cat_alias] is equal to categorical_indices, do not report the warning.
-                        if not(isinstance(params[cat_alias], list) and set(params[cat_alias]) == categorical_indices):
+                        if not (isinstance(params[cat_alias], list) and set(params[cat_alias]) == categorical_indices):
                             _log_warning(f'{cat_alias} in param dict is overridden.')
                         params.pop(cat_alias, None)
                 params['categorical_column'] = sorted(categorical_indices)