fixed lint issues and removed extternal libraries from flake8

Author: ragrawal

tests/test_dataframe_mapper.py

@@ -828,6 +828,7 @@ def iris_dataframe():
         }
     )
 
+
 @pytest.fixture
 def cars_dataframe():
     return pd.read_csv("tests/test_data/cars.csv.gz", compression='gzip')
@@ -881,7 +882,6 @@ def test_with_car_dataframe(cars_dataframe):
     assert scores.mean() > 0.30
 
 
-
 def test_heterogeneous_output_types_input_df():
     """
     Modify feat2, but pass feat1 through unmodified.

tox.ini

@@ -1,3 +1,15 @@
+[flake8]
+exclude =
+    .git
+    __pycache__
+    docs/source/conf.py
+    old
+    build
+    dist
+    *site-packages/pyflakes
+    *site-packages/_pytest
+    *site-packages/dateutil
+
 [tox]
 envlist = {py36}-sklearn{23}-pandas{1}
 
@@ -13,5 +25,5 @@ deps =
     sklearn23: scikit-learn==0.23.1
 
 commands =
-    flake8 --exclude build
+    flake8
     py.test README.rst tests